Bootmato - A unique eBook marketplace, Bookmato allows readers to purchase books a section at a time. 

Bookworm - Open ePub Books - Bookworm allows readers to add ePub books to their online library and read them on their web browser or mobile device

Diesel eBooks - Standard ePub format eBook seller.

eLibrary - Open Ebooks Directory - includes most of the eBooks sold on the internet. Free for addition of one's own eBooks.

Kobo Books - Standard ePub format eBook seller.

Project Gutenberg - Download over 33,000 free eBooks to read in various formats.

Smashwords - A treasure trove of indie eBook authors and publishers