KaraFun - KaraFun is the best online karaoke. Over 35,000 karaoke songs, with studio quality, at home or on the go. Regular updates. Free demo!
Revoice Pro - Revoice Pro is an audio plugin used for vocal tuning, time correction and ADR.
Sing! Karaoke by Smule - Karaoke with your favorite celebrity singers
GSnap - With GSnap you can get an auto-tune effect.
Yokee - Karaoke to YouTube videos
n-Track Studio - Audio recording and music creation app for iOS.