On my summer break while visiting friends in Sarasota I went to the Sarasota Classic Car Museum. In there i was pleasantly suprised to find a demo that you can play with that was the drivesystem from the 1908 Cartercar. Its a really simple friction drive CVT. Clickthrough to the YouTube video of it in action, its a nice easy way of showing what a CVT is and how it works.
http://youtube.com/watch?v=trJ09GSKv1g