Suspension Help

I guess this is the right place to put this. A friend of mine is going to be lowering his car soon and wants to use airbags or hydrolics. Basically, I know nothing about either one, so I'm asking for some web-sites that explain how each works, good applications for each, and pros and cons of useing each one. He doesn't want to use the hydros for bouncing around. He wants the car to be really low when it's still, but be able to raise off of the ground so it's still drivable. The car is a 2002 Camaro. I'd like some sites that I could link him to so that he will have a better idea of what he wants.