I just read a magazine article which gave a broad description of a CVT that Toyota is working on. Although CVT's are banned, this is a neat solution in getting rid of the slipping cones and belt.
Between the engine and rear differential, a planetary gear is installed.
http://auto.howstuffworks.com/gear-ratio4.htm
Just one gearset, and the interesting twist is that the planet carrier is attached to an electric motor, instead of being fixed. By varying the speed of the electric motor (and thus planet carrier), the final gear ratio is altered.