EarMaster - Professional software for ear training and practical music theory on Windows and Mac.
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
LenMus - LenMus is a free program for learning music.
Transposr - A free and simple way to transpose your sheet music or MP3.