The Humble Bundle started as a set of indie games for which gamers could pay what they wanted to pay, and the proceeds benefit charity. Humble is now offering an ebook bundle as well:
http://www.humblebundle.com/
The books in the bundle are:
Little Brother by Cory Doctorow
Boneshaker by Cheri Priest
Spin by Robert Charles Wilson
Shards of Honor by Lois McMaster Bujold
If one elects to pay more than the average, one also gets The Last Unicorn: Deluxe Edition by Peter Beagle and Just a Geek by Wil Wheaton.
The books are DRM free and available in the usual mobi, epub, etc.