The File Format Commons started when I was working on rendering files of various types. I needed a bunch of different sample files to work with and had a hard time finding them. So I made them. So far there are over 60 sample files of various file types on the File Format Commons. Over time I will be updating each page to include detailed file type information.
This site is still very much in progress and updated frequently. Please let me know if you have any questions or see any problems. Email me at alexschiller (at) gmail (dot) com.