Good luck with that. I've tried Craigslist and the swap meets, and they are usually just crappy bikes that weren't any good to begin with. I looked at one bike that was listed as "Like new", "perfect condition" and found wobbly wheels, a loose headset and a missing brake cable. It wasn't worth the asking price and I talked the seller down. Even then, it was a low-end Trek, and in the end it probably wasn't even worth what little I paid. At least I'm handy with a spoke wrench and got the wheels in shape.

Just remember this: If it looks like a deal but needs to have some parts replaced, the total cost of bike+parts will exceed the value of the bike in most cases.