Open Directory Project

The Open Directory Project is the largest, most comprehensive human-edited directory of the Web. It is constructed and maintained by a vast, global community of volunteer editors.

The web continues to grow at staggering rates. Automated search engines are increasingly unable to turn up useful results to search queries. The small paid editorial staffs at commercial directory sites can't keep up with submissions, and the quality and comprehensiveness of their directories has suffered. Link rot is setting in and they can't keep pace with the growth of the Internet.
Instead of fighting the explosive growth of the Internet, the Open Directory provides the means for the Internet to organize itself. As the Internet grows, so do the number of net-citizens. These citizens can each organize a small portion of the web and present it back to the rest of the population, culling out the bad and useless and keeping only the best content.

http://www.dmoz.org/