Dot What?! - Database of file extension information. Supports users comments and submissions. Includes discussion forum.
File Formats Magic Database - Contains information on main file formats as well as an FFID registry and a signature file permitting the identification of files from their contents. Also contains tips on how to design new file formats.
File-Extensions.org - Searchable file extension list including descriptions and associated applications.
FileInfo.com - Database of file extensions with information about each file type.
Filerecon Project - Developing a program to automatically identify files from their content. Project news, FAQ, and download. [GPL]
FileSuffix.com - A searchable filename extension database.
FILExt - Searchable database of file extensions for data formats, with information and notes on each.
Macintosh Type/Creator Database - A database of windows file extension codes with correlating Macintosh Type/Creator code pairs.
UK National Archives PRONOM Technical Registry - Resource for those requiring definitive information about the file formats, software products and other technical components required to support long-term access to electronic records.
Uniblue File Extension - Searchable database of file extensions, explaining what they are used for and which programs they are associated with.
