Since the Kevin Smith and Broken Lizard movies have already been recomended I would absolutely suggest Eulogy. It's a dark comedy about a dysfunctional family that has just lost their father, and how they are getting ready for his fueneral. It's hillarious plus an extremely well done movie.
If you're in to really dark comedies, Green Butchers is a good one. It's about these two danish butchers that accidentally lock an electrician in their freezer and end up serving him to their customers because they run out of meat. Well everyone likes the taste of human so they have to keep killing people. Funny, but again, very dark.