as I had to learn the circle of fifths myself lately I wondered if there are any free learning tools around on the net. I didn't find one and programmed one myself. Please take a look here and tell your students about it, in case you like it
This is an amazing site. I have tried to learn music theory from other sites in the past, knowing it is some really useful stuff and to be a professional means I am going to have to learn and understand it anyway. Most of those sites are way too hard to understand. I end up getting frustrated. With your site I actually enjoyed learning about the circle of fifths. I learned half of it yesterday and today I will finish it.