1. Bejeweled Blitz on Facebook. I think there's a non-Facebook version around too but there's nothing better than beating
2. Pac-Match-Party. This is a hybrid of Pac-Man and Bejeweled. Since the Bejeweled formula is such a winner, you can't really go wrong. Especially when Pac-Man is involved. This free flash game was created by Namco for Pac-Man's 30th anniversary.
3. Mirrors Edge 2D. A 2D version of the 3D parkour-style game for XBOX 360 and PS3. Heaps of fun. Controls really well and gives you a sense of what to expect from the 3D game.