vlc -- the VideoLAN Client

VLC media player is a highly portable multimedia player for various
audio and video formats (MPEG-1, MPEG-2, MPEG-4, DivX, mp3, ogg, and
more) as well as DVD's, VCD's, and various streaming protocols. It
can also be used as a server to stream in unicast or multicast in
IPv4 or IPv6 on a high-bandwidth network

WWW: http://www.videolan.org/