I've been converting my friends to the love that is Josh & Donna, so I put together this little write up...hopefully it will convince others to jump on the shipper bandwagon...

Season 1:
Donna wasn't a regular but Aaron Sorkin (creator of 'The West Wing') wrote her into every episode after Brad Whitford got on his knees and begged to keep her. :-)  There are a few moments that are worth noting...

• Episode 1 - The Pilot  
  The very first Josh and Donna scene.  Josh did something stupid and word is that he's going to get fired for alienating the religious right, but in comes Donna to talk to him.  We not only get a little J/D history lesson and learn her real name, but we get to hear her tell Toby (The Communications Director) to "shut up" and how great is that??TWW0101_01_Coffee
• Episode 5 - Crackpots & These Women
  TWW105_01_SeekToControl - early morning Josh and Donna funny
  ...but then Josh gets a secret card with directions on where to go in the event of a nuclear attack...and realizes that it's just for him and not his assistant - so he goes to talk to Sam about his card and his assistant, Cathy ...
  TWW105_02_YourCard
  In an effort to sort out his emotions, Josh makes a visit to his shrink, Stanley, and we first learn about the death of his sister.  TWW105_04_Joanie
  At the end of the day, there's no going back for Josh and his decision about the card - TWW105_03_TheseWoman
• Episode 10 - In Excelsis Deo
  It's Christmas in the West Wing and Donna knows what she wants - skis, gloves, boots, snow suit... no, she doesn't ski but she tells Josh she wants to learn.  He goes shopping with the President to a rare book store and comes up with something better - at least for the fans.
  TWW110_01_TheBook
  

Season 2:
Opens at the moment we ended Season 1 - with shots being fired at the President as he leaves an event.  He is, of course, shoved into the limo and whisked away - but the staff is left behind to find each other.

• Episode 1 - In The Shadow of Two Gunman, pt 1
  TWW201_01_Josh - is Toby looking for and then finding an injured Josh
  TWW201_02_Donna - is Toby telling Donna about Josh
• Episode 2 - In The Shadow of Two Gunman, pt 2
  While overlaying the drama of the President and Josh - we see through flashbacks how the current staff came to work for Bartlet...
  TWW202_01_DonnaHiresHerself -   This is Donna's flashback on how she joined the campaign.  It's important to note that in the script, the last scene has a note that says "Donna holds the badge and smiles because it's the first piece of jewelry that anyone has ever given her."
  TWW202_02_FatherDied - Another flashback to Bartlets staff winning the Illinois Primary.  Bartlets first run at the Presidency was also a Santos-like longshot, so there are a lot of parallels.  This scene is important because of next week's episode with Leo dying.  The series up to this point has set up that Josh looses people and feels responsible...  His sister died in a house fire when he was 5 and she was babysitting him.  She tried to put it out while he ran out.  His father, an old friend of Leo's, was fighting cancer and getting chemo, but died suddenly from a pulmonary embolism the day of the primary.  This is Donna breaking the news.
• Episode 9 - Galileo
   Josh has the task of deciding who will be on the next postage stamp, which means that Donna has the job of telling him how all of that works.  But he's got another idea.  TWW209_01_TheStamp
• Episode 11 - The Leadership Breakfast
  TWW211_01_BuildAFire - has intermixed J/D doing the funny side of them...It was the entire teaser (the 4min intro to each episode) and I included it because it never fails to make me laugh.
  TWW211_02_KarenCahill - this is the set up to the underwear scene - Sam, like everyone else, gets flummoxed by Karen Cahill and asks Donna to help get word to her that he really DID know what he was talking about.
  TWW211_03_Underwear - Adorable...simply adorable.
• Episode 14 - The War at Home 
  Donna's been acting funny and, as always, Josh seeks Sams council and we get honest proof of something long suspected.  TWW214_01_DateSabotage
• Episode 18 - 17 People
  Easily the most defining JD moment up to this point.
  TWW0218_01_Flowers - Josh sends Donna flowers for what she calls their "not" anniversary but it sets up a heart to heart...
  TWW0218_02_RedLights - Believe it or not, the context of this talk shows up at the end of Season 5... 3 years and shippers everywhere got it.  It was GREAT.

Season 3
The President Lied.  Season 2 ended with the public acknowledgment that President Bartlett withheld the information during the election that he has relapsing remitting Multiple Sclerosis. 

• Episode 1 - Isaac & Ishmael
  Not so much about Josh and Donna, but another insight to Josh as he tells a group of high school students about his mother and the box she has him keep in case of emergencies.  TWW301_01_TheBox
• Episode 4 - Ways & Means 
  Its time for government to investigate the lies and Donna's been working on her filing system all night when Josh finds her.   TWW304_01_WhiteCollarCrimeBoy
• Episode 5 - War Crimes  Its Donna's turn to testify but there's a problem.  When asked one particular question, she lies.  Already a big problem, it gets bigger when one of the lawyers, whom she had a brief fling, tells her that he knows she lied.  Whats worse than lying under oath?  Having to tell Josh.  TWW305_01_TheLie 
  Josh is mad, but never mad enough to not help her.  He comes up with a way around it thats probably less than legal, but will get Donna out of her situation.  TWW305_02_JoshsFix

Season 4
After spending most of Season 3 having to watch Josh date Amy Gardner (ick ick), Donna finally gets a boyfriend...a Navy Commander named Jack Reese (played by Christian Slater).  The relationship lasts from Episode 8 until 14, with Josh growing more and more obvious to everyone but Donna about his growing jealousy.  Jack gets new orders, transferring him out of the White House which leads to...

• Episode 10 - Holy Night
  It's Christmas Eve and Josh has a one track mind about Donnas holiday plans.  TWW410_01_TheInn 
  The President has plans too, to completely rewrite the Federal Budget before it goes to print in 7 days and Josh is going to need Donna's help.  TWW410_02_DonnaStays
  It's not looking good for Donna leaving for the Inn, but she's only dwelling on something Josh said earlier.  TWW410_03_WhatDidYouMean
  Much to Josh's disappointment, Leo tells him he's off the hook and that he's sent Donna on her way to meet Jack.  TWW410_04_GetItTogether
• Episode 11 - Guns Not Butter 
  Josh takes funding for 'remote prayer' to the President in a last ditch effort to get a bill passed.  Donna consoles him with a story about 'Fish hooks McCarthy' and how remote prayer might have benefitted him.  TWW411_01_Fishhooks
• Episode 15 - The Inauguration
  TWW415_01_Snowballs -There's a bad quote given to a reporter that ends up getting printed.  Donna claims it was her and decides to not go to Bartlets second Inauguration out of shame.  Josh never believes it was Donna and, while talking to reporter Danny (played by Timothy Busfield), he realizes he has proof it wasn't her and goes to confront her... with his posse: Toby, Danny, Charlie, and Will.
• Episode 21 - Commencement
  TWW421_01_GetJosh - Donna has a beer induced discussion with Amy Gardner, who Josh dated in Season 3 and who reappears in Season 4, episode 18 working for the First Lady. Donna's contempt for all things Amy isn't very easily hidden, much like Josh's was for Jack Reese

Season 5
This was a tough season.  Josh fell out of grace a bit with his job early on and Donna wanted more responsibilities, but she was the one thing constant for him.  She pulled him out of every funk from party turning Congressmen to a total shutdown of the federal government.  We were rewarded at the end of a tough season with Episodes 21 and 22 - Gaza and Memorial Day.

In episode 19 Josh gives Donna the chance to grow in her job - he sends her on CODEL (Congressional Delegation) to Gaza to listen to the peace talks and brief him and Toby about it.  Also going on the CODEL is Andi, Toby's ex wife and mother of his twins. The beginning of Episode 21 will change them both forever, when the CODEL becomes a terrorist target and one of the cars is blown up...the one carrying Donna.

• Episode 21 - Gaza
  The teaser is the explosion and when the episode starts we see Josh on an airplane reading email on his computer - obviously detached... then we go to the White House, going back in time to an hour prior to the explosion so we can see them finding out.
  TWW521_01_TheCodel
  
  Clips I didn't do between those previous scenes and the next one are:
  * Josh on the phone using "I work at the WHITE HOUSE and I'm trying to get information on Donnatella Moss!" on several occasions.
  * Toby getting calls from the Democratic party about who should fill the dead Congressmen's spots and Toby telling Will that they are calling him instead of Josh because they thought Josh would be too upset about Donna being in the car (even though Toby's ex was almost 'nearly' blown up).
  * Josh calling Donna's parents and telling her mom that's all the information he has right now but that he "didn't want you and Mr. Moss to have to worry" that he wanted them to at least know *something*.
  * Then Josh walking to this next scene with everyone falling in behind him and asking how Donna is and that all he knows is that she's in serious condition with bleeding issues.  Which leads us to...
  TWW521_02_KillThem - Josh has a nutty and Leo calls him on it.
  
  Throughout the episode and up this next scene, we've seen Josh on the plane to Germany reading emails that Donna had sent him and seeing Gaza through her eyes and voice in the emails she sent.  But now Josh is in Germany and we're back to the present:
  TWW521_03_Germany - introducing Dr. No Biggie and an introspective Josh.
• Episode 22 - Memorial Day
  TWW522_01_DonnaWakes - Donna wakes up and Josh is right there.
  TWW522_02_UhOh - Josh realizes that Donna's got a new Gomer (what he frequently calls anyone she dates)
  TWW522_03_ColinJosh - Jason Issacs is yummy and it's fun watching Josh's reaction to him with Donna
  TWW522_04_NickDanger - a continuation of the previous clip, but pieced together so we see what the note says translated.  Josh talks to Kate (the deputy National Security Advisor) while Donna listens in and comments.
  TWW522_05_Complications   -The end of the episode had 2 parts of Josh after his secret meeting following the previous clip.  I put both sections together into this clip.  Special notes to take...
     * once again he's throwing around The White House to get what he wants because he really has no claim to Donna other than being her friend and boss
     * Josh runs right through a door with a big red sign that says "DO NOT ENTER" - effectively not stopping for a red light. ;-)
     * Donna is facing the exact same condition that killed his father.
  
  That was our season cliffhanger...can you believe it?????

Season 6

• Episode 1 - NSF Thurmont
  NSF Thurmont is the military name for Camp David where Bartlet is going to have his peace talks.  While the staff prepares to head there, Josh is still in Germany...
  
  TWW601_01_Scared - Colin and Josh wait and Donna wants to see Josh.  Important here is that she knows what's happening and, having been there, knows it's what killed his father...plus Josh gets 'queasie' but nothing is going to stop him from walking into that O.R. to see Donna.
  TWW601_02_WeWorkTogether - even Colin has figured out what Josh is still trying to misdirect back to 'we work together'...but that's pushed aside by Colin's 'Lessons in Love' and another complication for Donna.
  TWW601_03_Still Here - Donna wakes up and fangirls everywhere scream...
  
  The next episode had Josh returning to The White House saying Donna "kicked him out" but that her mom was there - as was Colin...and a couple of eps after Donna comes home and back to work...but that's where the problems start.  Donna is more sure than ever that she wants more and uses her job as the driving force, but logically it's because she can't say - put me in a new job so I can date Josh.  

He, on unsteady footing, goes back to trying to be 'them' - but the dynamic has changed.  They both know it, but neither knows what to do.  Midway through the season, Donna quits and then Josh quits and they both go to work for opposing candidates for the Democratic ticket.

Josh picks a one term congressman from Texas - Donna works for VP Russell (who Josh HATES).  They run into each other on the campaign trail but neither knows what to do.  We end Season 6 with the Democratic National Convention where Santos wins, Russell loses, and the only time we see J/D in the same room is at the end when he brings her a beer.

All Josh & Donna clips from Season 6 are available on the Season 6 highlight page

Season 7

We open with Donna looking for a job with Josh and he shuts her down...which was a big OUCH moment but garnished 'If you don't think I don't miss you everyday..." from Josh.  Donna is gone for like 6 episodes when Lou hires her without telling Josh. :-)  all those clips are on my Season 7 West Wing page

So that pretty much catches you up... Once Donna got back with the campaign and Josh got used to her being there, you saw him leaning more and more on her because he trusted her and knew she'd get it done...whatever he needed.  One episode in season 7 you should probably see is 'The Wedding' where the Democratic party wants Santos to replace Josh as campaign manager because of an unexpected rise in Illinois polling numbers...they think he screwed up by not seeing it before it happened.  They are ONLY two people who go out of their way to find Josh to see how he is... Leo and Donna... and Sunday he's going to lose Leo. :-(