Go to forums.vwvortex.com -> Volkswagen classifieds -> Wheel and Tire classifieds -> 5x100 Classifieds.
They have a massive volume of wheels in our specs (5x100, 57.1mm centerbore, 35-38ish offsets) and lots of super awesome BBS setups that cost three times more than my car. Some of the wheels aren't to my (well most people's) taste, but there are a lot of nice sets. Prices are usually OBO and fairly low.
I bought my winters from there [lightly used], mounted to 15" jetta stock wheels, for $425 shipped. They fit perfectly, look cool, and function well. Just bought 17" summers with 2000 miles for $430 shipped and I'm waiting for them to arrive.