An Oldie But Goodie

Ricci Adams' musictheory.net is an amazing site. I have been using it with music students for many year. Think of this as a bit of nostalgia.

Ear Training

I am not a big fan of freeware, much more of a 2.0 guy, but this is a great tool for music educators. The basic version is a note recognition program. The advanced includes intervals. Amazing stuff.

Tetoria

A nice music theory website that includes exercises and tutorials.