Kobo Books - Kobo Books is a best in the class eBooks and eReadering apps for many reasons.
AbeBooks - AbeBooks has millions of new & used books, rare books and out of print books.
DealOz.com - Save time. Save money. Discover. Search new and used books, textbooks, and ebooks using the most trusted shopping comparison site, DealOz.com.
Occupy the Bookstore - Chrome extension to easily surface cheaper textbooks
calibre - Ebook manager, viewer & converter
Harlequin - Harlequin is a bookstore that sells paper books as well as eBooks. The store mainly deals in the genre of romance novels.