I'm also curious to know about it. But so far, couldn't find the best way to promote my next project that is online classified site. May be i will sell it.
It's probably going to take sometimes to get yourself out there but maybe a fanpage in your local area or a few run from small magazines or local newspaper might boost you up. Good luck!
You got to have something special to compete with those giant classified websites. Take a look at 123exchanges. Maybe you can get some new ideas.