I stumbled across this the other day. Baen (great SF publisher) gives away cds in some of their hardback books. Since I always buy ebooks from their webscriptions I figured I would never get one. But if you buy the same title that has cds from webscriptions you also get access to the cd iso and all of the free books. But beyond that those cds are legal to distribute for free. So there is a site that has them all compiled so you can browse and download directly.
Some of the stuff is in the free library, but most is not, and there are a couple of audio books on there as well.
Go to
http://files.plebian.net/baencd/
Enjoy