Some free techniques of bringing in traffic to your site are Twitter, Facebook, YouTube or any of the other video websites, UsFreeAds, CraigsList, web forums that are related to your products, free blogging platforms like Blogger or WordPress, safelists (depending on the service you offer), keyword-targeted PR releases, traffic exchanges, article promotion to EzineArticles and other article directory sites, and more. The good thing about this kind of advertising is that you only spend what you want to spend. You bid on certain keywords or keywords and then you get charged only when somebody clicks on your ad. If you don't have plenty of money to spend, make sure you choose the lower-searched keywords so you can bid lower. You can find all the stats on keywords in the search website free research tools.
Another paid options is Ezine advertising. Ezines are online magazines. The most effective kinds of ezine advertisements are called "solo ads" which suggests that your ad goes out alone (with no other adverts) and with your own e-mail subject line, not a common subject like "Newsletter number 20" for instance.