Other
Tone Savvy
You will find many free games that will help you develop your music theory knowledge. Learn rhythmic dictation, key signatures and intervals as well as several other topics concerning music theory.
Other
Music Theory First Aid for Struggling Students
This site provides music theory information on such topics as rhythm, intervals, scales, chords, etc. Also, there is a fine section which describes the basic concepts of form and structure.
Music Theory
Music theory.net
An online beginning music theory and ear training site. This site is for students to use at home to reinforce what they learn in class.