VanBasco Karaoke Player is free software to play MIDI Karaoke files. Lyrics can be displayed in full-screen. It allows to modify the tempo, volume and key of a song. It requires program installation on the computer.
The British Council site for English learning resources includes many songs accompanied by pictures, useful for sing-along activities. LearnEnglishKids Songs. Some guidelines and teaching suggestions are given in this handout.
This text gives 10 reasons why to use karaoke in the EFL classroom.
Furthermore, many videos with songs and lyrics can be found on the Internet. Thse are several examples:
Beauty and the Beast (just lyrics and tune)
All My Loving (Beatles, lyrics and tune)