There are also the four "Cities in Flight" novels by James Blish -- I remember reading these as a young lad, but I can;t really recall much about them...
...I seem to recall picking the firs tone up again about 10 years ago, but finding it not-so-interesting... but maybe I'm mistaken...
One great series by John Varley that I read recently is Red Thunder (2nd and 3rd books are Red Lightening and Rolling Thunder), which involves a hollowed out asteroid turned into a Generation Ship. There's a lot of great stuff in this series.
Another that comes to mind is the Ringworld series (Larry Niven). The Ringworld itself could be considered a Generation Ship, but the Puppeteers also added drives to planets, and used them to escape the collapsing center of the galaxy! Great books.
There was a late 70's Canadian TV series called 'Starlost' featuring Keir Dullea, from '2001: A Space Odyssey'. Personally, I found that it dragged but the show did get a loyal following. Maybe I'll feel differently about it now, no longer being 10 years old ... :)
Starlost was significant in that its generation ship, which featured large dome-shaped botanical pods, is probably the most recycled image in TV and films!
Arthur C. Clarke and Gentry Lee wrote three sequels to Rendezvous with Rama - Rama II, The Garden of Rama, and Rama Revealed. These span 3 (or was it 4?) generations of the progeny of the central character, one of a small group who became trapped while exploring the 2nd Rama.