There are also other good products on the market, but I'd recommend reading everything here and doing what they say ...this stuff works:
http://www.zainostore.com/Merchant2/merchant.mvc
I got the Mr.Clean thing to see what it's about and I've used it three times so far. First time I used it with the soap they give you but after I thoroughly washed, waxed, and polished my car I stopped using their soap since people told me (and I saw it after my first wash) that their soap removes too much wax which I don't need most of the time.
IMO, the most important part of the Mr.Clean setup is the last ultra-pure filter spray. Since it removes all carbonates and other particulates in the water, it does not leave any water spots at all after it dries. If you want to dry the car by hand every time, it may not be worth the price. But if you're sometimes in a hurry, spray it off with the last fine filter and let it air dry = no spots anywhere even on glass.