Not by posting ads but by responding to the ads? We built a craigslist responder tool that automates the process of responding to postings/ads on craigslist. eg if you are a real estate agent, you can use this tool and setup your campaign to send an email about your service to all the "owners" who are posting ads on CL to buy and sell the property.. just wanted to have an opinion of community here on how they use craigslist? This is the tool we built - CraigslistResponder