Allow me to just share my excitement at finding www.musicalcreations.com where you can download Karaoke mp3's - and they have the Pocket Songs catalog which features the most broadway karaoke out there.
The price is a little steep - $8.00 a song. However, there are alot of albums with only 1 or 2 songs on it I want and sometimes I need a song FAST!!! You can also make your own Karaoke cd's for $5 a song plus shipping, and it is linked from that website.
They have lots and lots of Karaoke from all genre's! Hopefully this info will be useful to someone.