Just because you build it, doesn't mean they will come. Drupal has several modules that help you build a site that have a good chance of being found by a person using a search engine. You can start with the SEO Checklist module (http://drupal.org/project/seo_checklist). "It provides a checklist that helps you keep track of what needs to be done." Check out Drupal 6 SEO - Drupalcamp Colorado to learn more about SEO for your Drupal site.