Had great fun with this program at New Years Eve
http://www.sourceforge.net/projects/ultrastar/
If you have songs you want to karaoke but UltraStar doesn’t support them you can easily (kinda :)) be created. Follow these instructions.
I must confess that I have had some preconceived thoughts about singing karaoke - but I stand corrected. It’s really funny! Will be a standard-item on parties at my house from now on.