Yesterday, I mentioned that Wits & Wagers is a great trivia game (while not really being a trivia game). I should have also mentioned two great party games that have always been a hit for me: Morphology and Time's Up.
Morphology is a great game for creative thinkers, sort of Pictionary with items. It was designed by Kate Ryan Reiling, who also published the game independently. (You can read my interview with Reiling here.)
Time's Up is an often uproarious game in which players compete (in teams) to name celebrities, authors and other well-known figures over three rounds of increasing difficulty.
Both are excellent party games.