Leanpub

theMage: Leanpub is a platform to create and publish ebooks and online courses. It is also a good place to find ebooks drm free.

Lulu bookstore

theMage: Lulu is an independent bookstore, and allow writers to publish their own books, both in digital or electronic format.

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.

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.