Bookmarks
Open Books
theMage:
Open books is a ebook store where you can buy ebooks without DRM - it is also one of the first ebook stores where you can download the books and later pay what you want for the books.
Smashwords
theMage:
Smashwords is a big indie ebook publisher. It helps writers publish their books, not only to their store, but also to other marketplaces and is one of the biggest sites to buy ebooks.
Lulu bookstore
theMage:
Lulu is an independent bookstore, and allow writers to publish their own books, both in digital or electronic format.