Tor has been running a promotion for a couple of months now where they've had a new free ebook each week.
It's been to promote their new website at
Tor.com / Science fiction and fantasy / Weblog, short fiction, art, and discussion
This week the site went live so they have all those past ebooks, and a new one, available until Sunday.
If you like SF and fantasy get them now.
Hope you enjoy them.