It is also important to consider where your site is listed. The main search engine and directory listings are essential for most sites while some of the more specialist directories would be more useful for a particular category of site. As with all search engine marketing practices, it is necessary to remain clear, concise and focused to achieve high ranking results.

Submitting to the Directory of Theme-Related Links you can increase PageRank and traffic.
You'll get traffic from your link partners. Plus search engines give higher rankings to sites that are a source of information on a focused topic. These hub sites are popular with surfers. All the information they need is in one easy-to-use place.
Link Popularity & Exchanging Links
The best incoming links are from related, popular sites. Unrelated sites don't usually help your link popularity. Submitting and creating a directory is the easiest and fastest way to increase your link popularity.

Visitors that come in from link Theme-Related directory were already on a web site with a similar topic. They already have a good idea of what type of site you have. They'll come to your site because they're interested in what you have to offer. These visitors are more likely to buy something from you than visitors that come to your site by accident or through a trick banner.