Games are a great way to practice your music theory!

 

 

• http://www.musictheory.net

• http://www.musictechteacher.com/

• http://pianoeducation.org/pnokids.html (online kids piano community)

• www.teoria.com (good for older kids)

• www.coursera.com has free online courses taught by university professors on many different musical subjects (probably suitable for adults)

• https://www.truepeoplesearch.com/find/content-know-your-composers-famous-people-of-classical-music (some basic info about a few composers)