As of January 2016, online music theory courses include Fundamentals of Music Theory from Coursera and Music Theory 101 from Berklee Online. Additional courses include eTheory: Music Theory Fundamentals from the Eastman School of Music at the University of Rochester. The websites also provide course prices and times.
Coursera and the University of Edinburgh's Fundamentals of Music Theory provides a basic introduction to music over the course of seven weeks for online students around the world. Topics include pitches, scales, modes, chords and keys, as well as rhythm and form, functional harmony, inversions, cadences and sequences. The class operates by lecture videos, and a Coursera Verified Certificate or Statement of Accomplishment is available to those who successfully complete the course.
Music Theory 101 from Berklee Online is a 12-week online class that provides a basic introduction to pitch, rhythm, scales, intervals and harmony. Students even learn how to write melodies and play notes on keyboards.
The eTheory: Music Theory Fundamentals course from the University of Rochester takes four to six weeks to complete, and it enables first-year music students to learn enough to take music theory placement exams. The program also offers several writing, playing, listening, singing and conducting exercises.