Many of you above referred to this, but for those who don't know Eric's body of work.
As the 'editor' of Baen's free library, he has been one of the earliest and most vocal proponents of DRM-free ebooks, and is one of the driving forces behind the marketing concept of providing free back-list books in order to hook future customers. See:
http://www.baen.com/library/
for over seventy free books.