Did it ever happen to you? You've just downloaded a file and it has an extension you've never seen before? Here is your solution!
http://www.dotwhat.net/
This site has a big archive on different extensions. If you ever need to know "What extension THAT FOR?!", just visit this site and find it out!
I've always used FileXt (http://www.filext.com).
.what? .net.
http://www.dotwhat.net/list_s/extension_sex/id_2575/