I finally found a little spare time and as a result, the first version of my interactive circle of fifths is ready for you to play with. I'm working on a second version, which will include tidier graphics and sound. But for now, you will get the general idea and hopefully start to find it useful. And here it is:
The Guitar Master's Interactive Circle of Fifths
http://www.theguitarmaster.co.uk/article.php/interactive-circle-fifths