When you were a kid, you probably had a toy airplane. Once your parents had got it into your head that toy airplanes were not actually capable of real air travel and you stopped trying to throw them across the room, you probably picked it up in your hand and flew it around the room, doing elaborate loops and curves.
While mouthing airplane noises is now fully optional, Wii's positional and orientational capability gives you the ability to steer objects as they travel through space, whether through the air or on the ground.
Imagine flying a bi-plane in Pilotwings — you'll have to roll to keep from hitting that mountain, right? Hold your controller like a paper airplane, steady to go forward, sweeping your arm around to do increasingly impressive curves and banks.
Of course, you need not simply fly a plane around. Squeeze the B trigger to fire your onboard machine guns and take out your competitors. Just imagine playing this with your friends online with the Nintendo Wi-Fi Connection, pulling off increasingly crazy manuevers and getting bonus points for making your buddy crash into a mountain evading your shots.
On your marks, get set, go! There's a few possibilities for steering a car with Wii, but one of the most interesting is the concept of a set of steering handles that attaches to the port on the bottom of the controller.
Grip those handles and rotate the whole assembly in mid-air to steer. Pull off a Mario Kart-style drift by rapidly steering left, right, and then bearing hard left until your drift is complete.