All seven seasons of what is indisputably The Greatest Television Series in the History of Anything Ever.
Joking aside; it's a great price for this - less than £6 per season, and in HD. You can't find the West Wing on Blu-Ray, meaning that this is the only (legitimate) way to own the series in its full 1080p HD glory. I honestly can't recommend it enough.
There's 7.35% cashback on Topcashback, or 7% Quidco, too.
PS: I'd like to put in a good word for The Newsroom, Aaron Sorkin's latest television series, too. The first season is currently TV Series of the Week on iTunes (at £14.99 HD) and it's great.