smpeg is an mpeg decoding library, which runs on just about any platform. It comes with two sample decoders, plaympeg (console, no UI), and gtv, a simple GTK+ interface.
You can check out smpeg from Subversion via these simple instructions:svn co svn://svn.icculus.org/smpeg/trunk smpeg
You can see the web-based svn interface here
You can subscribe to the mailing list for smpeg and view list archives here.