by Greebo » Wed, 13Aug07 20:19
.rar is a standard Microsoft compressed file format that can be unpacked by a wide range of utilities, 7-zip being a prominent one (Google is your friend). Being a Linux user myself, I use the tools that come with the distro usually, which utilise the packages rar and unrar (or unrar-free if you're picky about things like that).
.gam is a game save file that would normally be accessed by the game that created it.