There are a few places that you can go online for rims.
Tires.com is a good one. They have a great interactive program where you can see what the rims would look like on your car. Pretty spiffy. They are kind of expensive though. Get a copy of Super Street magazine. Its an import mag but it has a lot of wheel advertisments in it. That is where you are going to get your best deal.
Wheelmax.com is a good place to see what the rims look like too.