Blogs can dramatically increase your Search Engine Rankings, because search engines scrawl through them also. Blogs are easy to create, it's as simple as creating an email account. Moreover, you can register with free blog hosting softwares like wordpress, Blogger, Typad, etc. to post your web logs. In order to make your blogs popular, comment on other blogs, submit your link on other blog rolls, submit your site to bookmark websites such as Digg, Stumbleupon, etc.
Blogs are one way to Increase Website Traffic, there are several other methods, which can enhance the rankings and ROI of your site.