Here are some ebook sites.
http://www.webscription.net/Default.aspx?
Baen books online store. Region and DRM free prices are superb.
https://www.fictionwise.com/
A good all round store some DRM and geographical restrictions, all multiformat books region and DRM free. Owned by Barnes and Noble
http://www.smashwords.com/
Good cheap independent online book store.
http://www.akwbooks.com/
Another independent online publisher I have read some excellent stuff from here.
http://www.waterstones.com/waterstonesweb/
An English store. Prices can be high but some things can be bought that are geographically restricted by the American stores. Sells paper and electronic stuff.
http://www.readwithoutpaper.com/
Australian apparently. Some good stuff. I have not bought from them yet but it is only a matter of time.
https://www.dadirect.com/
A Melbourne outfit sells ebook readers generally better known as suppliers to librarians and libraries.