Big news! Dungeon Defenders (with Steam key) is the headline game from May's IndieRoyale bundle! It's available until approximately May 9, 2012. The current price as of writing is just over $5 USD. The bundle includes four other games plus other content.
Fans of inexpensive, awesome games should keep their eyes on these bundles. Probably the best known is the Humble Indie Bundle which has included games like World of Goo, Braid, Trine (my #1 discovery!), Jamestown, and Super Meat Boy.
Unfortunately, searching for "indie bundle" on Google currently returns results mostly commenting on the irony of EA releasing an "indie bundle". (Interestingly, you can use quotes to signify both literal and sarcastic elements in the same sentence. Who knew?!) Still, there are some other bundles out there, and probably more will appear with the rising success of the Humble bundle.