VLC Player

VLC is a video playing software. This has recently replaced Quicktime as my video player of choice. It is a free and open-source video player that runs most video formats out there, everything from Quicktime files to DVDs (the latter assuming you have a DVD drive on your computer).

A partial listing of file formats that VLC can play includes AVI, MOV, WMV, Ogg, MP3, MP4, DVD, and DivX, just to name a few.

VLC Player runs on Windows, Linux and OSX.

Check out the VLC Player website