It is my goal to make a listing of common file extensions and what applications open them (properly). If you have a question, please feel free to respond to this posting and I'll update this post accordingly.

Extensions - Programs
.rar - Rar files can be opened with WinRar; these files are in a compressed "container" which is capable of holding many various files and compressing them so that they can be downloaded faster and take less space on your computer and the server which hosts the file.