UltraStar Deluxe - A free and open source karaoke game inspired by the Singstar™ game, runs on Windows, Linux and macOS.
SingPlay - SingPlay Karaoke Your MP3s developed and published by NexStreaming Corp.
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!
Midifun Karaoke - Midifun Karaoke created and published by Puasoft.
OpenKJ - Open source cross platform karaoke hosting software
iSing Karaoke - iSing Karaoke is free to use the Karaoke app that offers free access to hundreds of songs.