Theme, Open Directory Project listing (dmoz.org)

Theme
For spam-free and relevant results, search engines start evaluating sites as one page to find the main theme covering all pages of the site. Most major search engines have become theme-based.

Search engines extract and analyze words on all pages of a website to discover its theme. The more keywords found on your website that relate to the user's query, the more points you get for the theme. Therefore, if your Web business includes many products or services, try to find the theme that covers them all.

Open Directory Project listing (dmoz.org)
The ODP (also known as DMOZ) is the largest human-edited directory on the Web. Many major search engines use the ODP data to provide their directory results. This works because sites put forward for inclusion in the ODP are reviewed by real people who care about the quality of their directory.

It is still a good for a website to be present in the ODP. For new sites, it is an excellent starting point, because Google regularly spiders the ODP to update its own directory based on the ODP listings, and if your site is included, you'll get a link that Google believes important enough to start off crawling your site.

As well as the weight of a link from the ODP, it would be even better if the site were listed in the most topic-specific category to make the link not only important, but also content-relevant.