I have an airbrush (actually my ex wife now has an airbrush) and let me give everyone a bit of advice. Don't buy one of those little airbrush compressors, they don't have a tank so they need to pump continuously and they are very loud for their size. Instead, save some money by going down to the hardware store and buying one with a tank. I got a small one for around $30. make sure it has a pressure regulator, otherwise you will need to buy one so you don't blow 100 psi through the airbrush.
The great thing about the tank is that if you have pressure left over from the last time you used it you may not even need to plug it in to use it for small stuff.