We play a lot of those on game-lunch Fridays... also popular at our lunches:
Core Worlds ( http://www.boardgamegeek.com/boardgame/98351/ )
Quarriors ( http://www.boardgamegeek.com/boardgame/91536/ )
Infinite City ( http://www.boardgamegeek.com/boardgame/46807/ )
We occasionally have a Saturday game day among friends for longer games, but these three are great less-than-an-hour games. Core Worlds is about an hour, the other two will get you 2 to 3 games in in an hour.