Brandon Sanderson (co-author of "The Gathering Storm", the latest in the Wheel of Time series) has released a full book and a couple of short stories for free.

• Warbreaker
• Defending Elysium
• Hope of Elantris

http://brandonsanderson.com/library/

Sadly I don't see Firstborn on his website which I know Tor put on their website at one point...