It supports DVD,streaming mpeg, avi, asf, wmv, quicktime,mpeg 1/2, and DivX (both types). If you install the win32 codecs it will also play windows media 7&8. It is available for Linux, Solaris, and FreeBSD.
It is the best I've played with so far. One very cool feature is that it will capture snapshots of a video and save them as a png file with very good quality. Here are some screenshots [xine.sourceforge.net]
If you have Mandrake, this page [rpmfind.net] will be your friend. Here is the rpm [rpmfind.net] for the win32 video dlls. A zip of the same files is available on the mplayer site [mplayerhq.hu] which may actually be more complete than the rpm.