post on forums with your link in the signature, post comments on dofollow blog posts, and word of mouth are the best free ways. do some SEO work, link building, and a very popular way to get traffic is social networking.
Free directories is not my idea of marketing...more like a waste of time. For marketing I would suggest joining up with forums/blogs specific to your niche and contribute to the 'market' itself. Add input, write useful articles, basically donate your knowledge to others to gain your site recognition. Of course this is a fancy way of saying drop your links at similar sites, but it is a much better long term goal to actually spend time on adding value.
Look for forums that are in your niche and just put your link in your signature and stay an active poster on those forums. It will work out.