If you haven't checked out
http://www.boardgamegeek.com/ do so.
I recently picked up a few board games since I realized I was relying too heavily on my friends to bring games when I have a game day. The games I got are:
Roll through the Ages -- A resource game using dice, a wooden peg-board and a scoresheet. Only supports up to 4 players, though.
Shadow Hunters -- Can support up to 9 players, is really best with 6 or more. A straightforward game where you try to kill your opposing players, but everyone's identity is hidden at the start of the game. So you have to spend time figuring out who your allies are and who your enemies are.
Kill Doctor Lucky -- Supports 3-7 players. Basically think 'Clue' except you're trying to kill the old bastard.
I don't own it, but I do recommend Catan. I have Carcasonne on the Xbox, and have played the tabletop version as well, and I recommend that also. Dominion is pretty cool, if a bit expensive. There's also a Cranium card game called "Ziggity" which is a fun little side game.