I wrote about Ricci Adams’ MusicTheory.net a couple of years ago, but since then some new things have been added to it that are worth noting. MusicTheory.net still offers music theory lessons covering everything from basic note recognition to difficult chord inversions. The lessons can now be customized to test users on the notes and concepts they need to practice the most. MusicTheory.net also offers calculators and tools handy for composing music. And if you just need some staff paper, MusicTheory.net offers sheets that you can print.
MusicTheory.net‘s lessons and practice activities offer a range of difficulty wide enough for the site to be used by brand new music students and older music students alike.