Turn your PC into a very advanced MediaCenter/HTPC
MediaPortal turns your PC into a very advanced MediaCenter / HTPC. It allows you to listen to your favorite music & radio, watch and store your videos and DVDs, view, schedule and record live TV as a digital video recorder and much much more
Blastwave is a GTK+/C based GUI client for the XMMS2 Music Multiplexing System.
KSP is music player for Windows (working on Linux edition). At the moment it is very new and buggy so it contains only basic functinality and should be used only for development purposes.