Quite possibly my best purchase in 2010 was Humble Indie Bundles 1 and 2. And now, Humble Indie Bundle #3 (The Humble Frozenbyte Bundle), featuring Trine, Shadowgrounds, and Jack Claw, apparently goes on sale later today. It's a really clever ad, too.
If you have the option of spending a certain amount to also obtain bundle 1 and 2, you should jump at the chance. World of Goo alone is worth the purchase.