MPlayer is an open-source video player with wide support for many movie and audio formats.
Mplayer is quite simply the best multi-platform video player available today on any platform.
Supported video formats:
DivX, OGG, WMV, MOV, FLAC, XVID, Indeo, H.263 and so many more.
You'll need this as well, MPlayer-GUI by Daniel Westerberg, click here.