And don't forget www.baen.com they have been my favorite spot to get SCIFI and Fantasy books for years. Started with my Reb ebook reader through my Sony readers ,Pda,Kindle and now EE. EVERYTHING is available in multiple formats without restrictions no DRM! They also have most of my favorite authors. Their prices are great, you can buy books individually or in groups (webscriptions) even getting advance prepublication copies of new books. Nobody does what they do.

I have also used Fictionwise, they are almost as good and have a larger selection including drm'd books.