Video Lan Client is a MediaPlayer with support for many formats including DVD movies, DivX, and others, and runs on many platforms such as Linux, MicrosoftWindows, MacOSX, and more.
VideoLanClient is used by a number of third parties as well: eMule recommends it for previewing downloaded video, and Google Video uses a modified version of it.
There is also a VideoLanServer? that can stream such videocasts to a VideoLanClient located elsewhere.
The DebianLinux Package is vlc, and vls for the server. See AptSourcesList to enable more formats.
One page links to VideoLanClient: