Song Galaxy - Sing with the Stars! Backing Tracks out of this World. 6000+ Audio Backing Tracks 2000+ MIDI-files. Karaoke Files
Musicroom.com - Offers free shipping on orders over £15 and the largest choice of sheet music, tuition books, music books, music DVDs & videos, music software, music accessories and music for schools.
Karaoke Island - offer downloadable mp3 karaoke songs with a Freeware PC karaoke player, Midi-files with lyrics and karaoke software. Choose from 1000s of songs. New ones added constantly.
Crotchet - are a classical music specialist. They tend to have in their database titles not always available from the more general music stores.