Google provides access to a human-compiled directory of web sites, called the Google Web Directory. The information for the Google Web Directory comes from the Open Directory, so if you are listed with the Open Directory, you will be listed with the Google Web Directory. The How The Open Directory Works page explains more about getting listed with the Open Directory.
Accessing The Google Web Directory
Users are directed to the Google Web Directory via a "Google Web Directory" link that appears below the search box, on the Google home page. However, users are far more likely to encounter Google Web Directory information via the Google search results page.
Specifically, Google will present directory category links at the top of its results page, when relevant ones are found for particular searches. The area marked E in the example above, shows how two category links are presented in a search for "travel."
Some users are likely to click through on these category links, when they are presented. Because of this, being listed among the sites within a particular category may bring you more traffic.
You'll notice differences, if you compare a category at the Google Web Directory to its counterpart at the Open Directory. One reason is that the Open Directory listings may be fresher, as Google only updates its listings from the Open Directory every four weeks or so.
A much more important reason for differences is that Google ranks sites within its directory by "PageRank," which is a score that shows how popular the site is determined to be, through Google's link analysis system. For your site to rank well, you'd need to have a good PageRank -- and that means building links, as described on the More About Link Analysis page.
If your page is listed with the Google Web Directory, that will almost certainly help ensure that it is also included within Google's crawler-based index. This is because links from the Google Web Directory are considered very important in Google's link analysis system. Similarly, a Google Web Directory listing may improve your ranking in Google's crawler-based results, for particular searches. In addition, Google will display a category link for any page in its crawler-based results that also resides within the Google Web Directory.