Teoria
MusicTheory.net
Music Tech Teacher
Music Learning Community
Misicca - Learn Music Theory for free!
https://www.musicca.com/
Music Tech Teacher: Games!
http://www.musictechteacher.com/music_quizzes/music_quizzes.htm
Music Theory.net: lessons and practice exercises
http://www.musictheory.net/
Theta Music: Ear Training
http://trainer.thetamusic.com