MobileRead, which I believe is the web's largest site devoted to all e-reader devices.
MobileRead is an amazing trove of information, full of technical data and with separate sub-boards for different e-book readers and e-book software.
Of particular interest to Kindle users, the site is the source of much of the technical support information for the Calibre e-book software package.
Based in Europe, MobileRead has international sub-boards for discussions in different languages.
With 2.1 million posts over ten years, MobileRead is a leading site for a wide variety of e-book information. (KindleBoards.com, focused more specifically on Kindle e-readers, is close behind at 1.8 million posts!)
The site has limited viewing access for unregistered members, but if you're so inclined, you can register at the site and see what it has to offer. Click on the logo above to access the MobileRead site!