Put the word out
The last time I bought a car and wanted to get rid of my old one, I just put the word out everywhere I went. Mind you I just put the word out that I was buying a new one, not that I wanted to get rid of my old one. More people ask you if you're selling your old one and are interested than if they think you need to get rid of it. A waitress in a restaurant ended up buying mine because she "overheard" me talking about my new car and that I was going to probably sell my old one.