Brandon Sanderson is offering his novel Warbreaker as a free download.
What I like about this particular freebie is that he's not only making the final version available but previous versions as well. That's kind of a twist. How often do you get to see what pains an established author went through from first draft to polished final?
He starts with Version 1.0, which bears a warning:
this version is very, very rough. It includes characters that I decide to cut halfway through, has some serious lack of foreshadowing for elements at the climax, and contains a lot of typos. Read at your own risk!
You can make your way through versions 2.0, 3.0, 3.5, and, finally, 4.2, the latest and greatest. He's also got a Word doc which compares versions 1 and 2 if you want to see the differences side-by-side.
Sanderson is giving away Warbreaker under a Creative Commons license. The book will be available for purchase in June of this year.