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.
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.
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).
I don't care if this has nothing to do with interval ear training, I just found what this guy had to say about perfect pitch really interesting. I still have no idea if my pitch is actually perfect or not though haha.
List of famous songs to learn musical intervals. Create your own custom lists with the interval song chart maker. A perfect starting point for ear training.
This website helps recognize different scales by ear, without looking at what key it's in. This also helps greatly with hearing different trichords, harmonics, and melodic scales.
Sight Singing is supposedly one of the most difficult challenges on the AP Music Theory test and stunts many students. However, this site promotes voice, ear, pitch, theory, and rhythm training. With enough practice, this site will prove to be very useful. :)
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.
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.