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.
This site lets you practice identifying scales, chords, intervals, and chord inversions. There is also an app on the App Store that I'm pretty sure is free.
This website has practice exercises for everything from note dictation and clef reading to harmonic progressions and the construction and identification of seventh chords. The "exercise" page, which this link goes directly to, houses all of the practice resources.
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 website lists intervals and shows them on the treble clef. There are also tabs on the side to notation, rhythm, meter, tempo, musical form, scales, chords, and harmony.
This is a comprehensive study guide for many concepts within music theory. Given specific parameters, it will generate specific scales, key signatures, etc. It also has manuscript paper, glossary of vocab terms, and more.
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).