Turn the car off...?
That is the worst thing you could ever do. Shutting off the car will cause the pedals to lock as well as the fact that it will no longer let you steer. So while you've successfully killed the engine, you are still going the same speed, except now you can't steer to avoid walls, cars, ex.
The best thing in this situation would be to put the car into neutral. While the engine will start to race, no power will go to the wheels. You simply have to steer the car while you lose momentum. This will also let you use the brakes/Emergency brake. Once the car comes to a stop then you can switch off the engine.