It's worth remembering that you are not the only person that you know that buys cars. Often friends and relatives are considering buying a new car and want to get rid of their old one in an easy way. Make sure you let them know that if they are going to trade-in that you might be interested in their old car.
My brother's first car was a Subaru with 250K miles that our friend's family was replacing. Instead of trading it in my brother offered $50 for it. They decided to give it to him instead.
My first car was a Corolla that my uncle was going to trade in. I offered him the trade-in quoted price ($1500). Two years later I sold it for $3600 on Craigslist. I would have gladly sold it to a friend for $1500 though.
There are plenty of people that like to buy cars from dealers and do not want the hassle of craigslist and are willing to trade in. If you're in the market for a car, make sure your friends and family know!