I bought a set of tires and rims from Tire Rack -- tires on the rims arrived at my door in a couple days. Very cool and got a great deal!

Remember, if you order just tires, you will need to find someone to take off your old tires and put on the new ones. Some places charge quite a bit if they are tires you did not buy from their store. I would advise you to find out where and for how much it will cost you before deciding on a Tire Rack purchase for tires alone.