Lots of great games and courses. You need to join, but it’s free and that gives you access to the first three levels of the fantastic music and sound tech activities!
There are a number of well-chose, fun videos and activities on reading music and theory…
Free to use. This site contains lots of music theory lessons as well as theory exercises and ear training exercises. Customize your own exercises. Note recognition, key signatures, chords, scales, keyboard, guitar, aural… Also has apps for iPhone/iPad “Tenuto” and “Theory”.
Teoria has interactive tutorials, exercises and ear training.
Customisable interactive theory and aural training on an excellent range of topics. Free.