Yes, I wonder how Baen can afford to offer so many freebies, and many of their other books are a fraction of the Amazon/B&N price. Nor does Baen restrict people to official eReaders -- the books are available in PDF, HTML, and many other formats, so can be read on virtually any computer.
Two other great sources for free eBooks are
www.manybooks.org and
www.gutenberg.org, although their books tend to be much older -- great if you like PG Wodehouse or H. Beam Piper. There also are several membership sites that require a $50 or $100 payment up front, in return for fantastic bargains on modern books, but I'm leery -- you know the saying about too good to be true. So if any members of this forum have experience with such sites, I would be very interested. Same goes with experience with local libraries -- which I still haven't had the time to try.