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.
Flat - Online collaborative music score and tab editor, accessible from any device
Auricula - Practice your sense of hearing and learn to identify intervals for your musical development.
Transposr - A free and simple way to transpose your sheet music or MP3.