FileProInfo - It's All About Files, Software, Online Tools - 100% Free
Goodreads - See what your friends are reading.
File-Extensions.org - Large computer file extension library with detailed explanation of each file type with links to download free or associated software programs.
LibraryThing - A home for your books.
FileInfo.com - FileInfo is the central file extensions registry and contains a database of over 10,000 file types.
BookAuthority - BookAuthority collects the most recommended books on business, technology and science - as featured on CNN, Inc and Forbes