Try craigslist.com

Once you are on the site, you can select your closest city. You have to watch the bike section everyday. Most of the people selling "road bikes" are selling 1980 era road bikes with downtube shifters, but everyonce in a while, you can find a relatively new bike.

You could also call around to a few local bike shops (LBS as we call them here) and see if they have any closeouts. Theres a shop near me that builds alot of frankensteins - he buys bike kits from the manufacturers that have been canabilized at the factory for parts. The manufacturers auction these kits to the shops at the end of the year for much less then what the kit would be worth complete. Anyway, he then builds the bike up with parts from the shop's stock, and he sells the "frankenstein" for much less then what the OEM bike would sell for new.

You may even have a shop in your area that buys and sells used bikes. We have a few in Philly that do that.