VLC

VLC (www.videolan.org) a multi-platform video player which started as a student project, but currently is one of the most popular video players out there. It is more of a streaming solution than just a player (started as a client-server project), very nice user interface Current version has better support for cyrillic subtitles than mplayer which is enough for me. VLC is an actively developed opensource project which accepts contributions and donations.