Meludia - Listening exercises and to sharpen your ear and music theory skills
tonestro - Practice & improve on your wind instrument while having fun
GNU Solfege - GNU Solfege is free music education software.
Violin by Trala - Violin by Trala is a music learning app that is designed specifically for Violin users.
Auricula - Practice your sense of hearing and learn to identify intervals for your musical development.
Simply Piano - Fast and fun way to learn piano