One of the most common problems with web sites not ranking well or not receiving the traffic that they could involves inclusion. Most search engines can effectively find your site, crawl from link to link and include your site in their index.
Sometimes the format of a site or the url structure causes problems with indexing. Google Sitemaps and Yahoo Search Submit paid inclusion allow you a better chance for inclusion in search results. Now Yahoo offers a free alternative for submitting multiple urls.
There’s a more detailed post over at Online Marketing Blog about search engine inclusion options available for Google and Yahoo and how many sites can improve their chances of full site indexing.