How can I get traction for marketplace app?

www.meshipu.com

The last time I posed this question I got very little in the way of answers, instead I got a lot of advise as to why such a service would be a bad idea (drug dealers using, thieves...etc). I already considered all those issues before coding the site and considered them non-deal breakers.

What I really want is ideas on how one could get visitors to this type of site (perhaps really any site).

What sort of web forums might be useful? I have already being posting craigslist ads in the rideshare category.

I have thought about paying people to holdup signs on the side of major highways such as the New Jersey Turnpike.....Any ideas?

Please only ideas about generating visits, NOT advice about the worth of the website:)