FileProInfo - It's All About Files, Software, Online Tools - 100% Free
OpenWith Enhanced - OpenWith Enhanced description and features
File-Extensions.org - Large computer file extension library with detailed explanation of each file type with links to download free or associated software programs.
Open Any File - Rocky Sand Studio is passionate to create amazing apps for Mac. We've made several award winning utilities, popular news readers, desktop social apps. 20M app downloads, 800K daily users.
FileInfo.com - FileInfo is the central file extensions registry and contains a database of over 10,000 file types.
FILExt - Open, view and convert files online