www.virtualrc.com
The software is free plus two tracks.
The USB adapter plugs into your receiver and you control the game from your own transmitter.
The USB adapter is $29.95 with $20 shipping.
Basically 50 bucks, but if you figure the software is free its not a bad deal if it works well.
I think they have 8 or so additional tracks which you can buy.
You can also compete on line.