Free is always the best price and The Free Bundle #3 is now up for grabs. You won't have to open your wallet to enjoy Cube 2: Sauerbraten, UBERLEBEN, Ninja Senki, Armagetron Advanced, and Lyle in Cube Sector. Most of these games work on Windows, Mac, and Linux.
From the same page, you can also buy Vampires for $4.99. This is made by the team that created J.U.L.I.A., and their studio is in need of some financial help in order to keep running. All they ask is that you buy Vampires and tell your friends about this deal. So get get free games and help an indie developer out while you're at it.