So this site has a variety of different intervals, scales, chords, and some melodies that you can use to help you identify the different names of intervals, notes andmelodies. Also has a perfect pitch trainer to help you work on your inner ear.
This site talks about the different moods associated with different chord types. It can help narrow down the categories that a specific chord could be.
For those of you that don't own a piano, this app is a portable piano for your iPad/iPod/iPhone. This is really helpful for visually seeing where notes such as C4 and the other notes on the piano fit. It is also useful for practicing ear training (like we do in class).
An extremely cool and simple to use Synthesizer app. $1.99 on the App Store, and even for just messing around I found it worth the money. Very good app.