Free Karaoke Game - Ultrastar Delux aka Singstar

UltraStar Deluxe is..
A free and open source karaoke game inspired by the Singstar™ game available on the Playstation®. It allows up to six players to sing along with music using microphones in order to score points, depending on the pitch of the voice and the rhythm of singing.

Use any video filetype you want as background (youtube / flv, divx, mpg / mpeg, avi, ..). You can create and use your own songs, various are already available. Customize its look through themes and extend it with more party game modes via plug ins.

Download Ultra star Deluxe here
http://ultrastardx.sourceforge.net/
Get Songs here
http://www.ultrastarsongs.com/