I'd go for Great Dalmuti. It's a card game that's essentially Asshole, but with a totally different deck that really changes things. Instead of four of each number, there's one 1, two 2s, up to twelve 12s. It's incredibly simple to learn, there's a good deal of strategy, come from behinds are possible, if not easy, and games can go on for as long or short as you like. It can function as a filler if needed, or you can spend the whole night playing it, as I have on many occasions.
I think this game, and Dilbert, both have the same basic card mechanics and deck construction, are both products of Wizards of the Coast, and are both out of print. Might have to look around the net a bit for them. It's not the types of games you can grab at Toys R Us.
But dead on in the description, and hours of fun while killing time in undergrad between classes.