I always thought I had "a good ear" for music. I guess I was wrong. The Toned Ear site's ear training practices can test your musical hearing and also help you improve that skill.
The exercises include identifying intervals between notes, identifying chords you hear, naming a single note and identifying the scale degree of a note relative to the key established by a chord progression. (If you've studied music, you probably know what that means.)
The site recommends practising a little each day -- short sessions are good. Whether you're learning to play an instrument or are an experienced musician, the exercises at Toned Ear could help you train your ear.