Aside from Sam, Toby, and C.J. (and for the smart-alecks, Bartlett and Mrs. Landingham have pretty defined jobs as well!), the character's job descriptions aren't well fleshed out. I really want to see the organizational chart Josh's office is working on for Mandy!
Here you go.
Leo pretty much runs the West Wing, he manages everything so that the President is freed up to focus on important policy decisions, and as such his job is arguably more demanding than the President's. Leo is also the only member of of the senior staff to be involved in military decisions and sits at the President's side in the Situation Room.
Josh is Deputy Chief of Staff, which is a fancy title that doesn't seem to mean much. His main role is to direct political affairs, it's his job to push the President's agenda through congress and the various government departments.
Toby is the Communications Director, so he orchestrates the President's message and decides how it's presented to the public, although he rarely deals with the press directly. He's also the President's main speech-writer. Sam is Toby's deputy, and he works with Toby on the speeches.
CJ is the Press Secretary and it's indicated that she technically works under Toby, but in practice she does her own thing and reports directly to Leo.
Mandy's job is to annoy people while they're trying to do actual work. She answers to Josh and she answers to Toby.
Donna is pretty much Josh's secretary. Her role in the first season is to not understand how the government works so that Josh can explain everything to the audience.
Charlie is the lowest ranked of the main cast and has no official role in policy, but he works extremely closely with the President and has a desk right outside the Oval Office. His job is to be the token black guy.
In practice, Josh, Toby, Sam and CJ are equals and have easy access to the President without having to go through Leo.
The best thing they did was skip a year and go to the election. I wish they planned it better so the year didn't just disappear, but most people don't notice that.
I think a lot of fans noticed the missing year, we just didn't care if it meant avoiding another season like the fifth.
I've been watching donated R2 DVD complete set and quality seems pretty good, esp latter seasons.
My only problem with the DVDs is that season 3 is in anamorphic widescreen, which looks terrible on a widescreen TV. Also, the R2 DVDs have no special features, which is a pity as I would very much like to hear the commentary to Twenty Five
. Just what was going through Aaron Sorkin's head, leaving the show with such an insane cliffhanger?