Cash recently started an introductory course to agility. After another 4 weeks, we are changing trainers (I am not happy with this trainer) and then it is full-on agility. He is also starting flyball soon (as well as two more classes - one for obedience and one for tricks).
I think he is going to love doing agility. The energy factor also helps
Take a look at the videos of yorkies doing agility and flyball on youtube. It is amazing what these little guys can do.