I've had a few ideas for this. It'd likely be stuff on DVD, at my house - but I still need to get my hands on a multi-region/multi-standard player, so people don't have to all sit around my PC!

Last time I had a few people over, the Hitchhiker's Guide DVDs had just been released by the BBC for Region 2 (Europe) and, being impatient, I imported those rather than waiting for the NTSC/Region 1 release. And it was a pseudo-marathon due to the 3 hour runtime.

But other ideas would be:

Comedy fest: Episodes of Monty Python, Fawlty Towers, maybe things like Clue....

Disney fest: The collector's tin sets (Goofy, Mickey Mouse, Silly Symphonies), Black Cauldron, Fantasia (both of them), Winnie the Pooh.

Pixar fest: Toy Story 1 and 2, Bugs Life, Monsters Inc.

Animation fest: Tom & Jerry, Scooby Doo, Underdog - and DangerMouse and Duckula if I can get a DVD player that plays PAL (apart from my PC again). Those discs, fortunately, are region zero.

Sci-fi fest: H2G2 again, Doctor Who, maybe pick and choose some Star Trek episodes.... Oh and Tron perhaps.

Foreign fest: La Femme Nikita (new special edition), Wings of Desire, The Princess and the Warrior....