Bookzilla is a German online book shop with a great concept. The website is just a frontend to Libri.de – a big wholesale trader for books. However, any proceeds Bookzilla earns from selling you books are donated to the FSF. A really nice idea.
However, being just a store front for another shop can be problematic:
Bookzilla/Libri.de are selling e-books. They have many on software development topics. However, all e-books are copy-protected using the MobiPocket format. You can only read these e-books on devices that are supported by MobiPocket. Incidentally, Linux is not among the supported platforms.