Web Subject Directories
It is estimated that there are over 12 billion pages posted on the "Surface Web". Even Google - the largest search engine - indexes under 9 billion; so in reality any search engine can only find a fraction of available Web content. Another 200+ billion pages are buried in the "Deep Web," database-driven content that search engines cannot crawl.
Most search engines are designed to meet the needs of surfers looking for news, sports, weather, chat and Web sites about their favorite media personality. So, how can you find the factual, subject specific information you need for research purposes?
Use subject specific directories or subject trees, guides that are designed by real people who know the subject and can uncover those hidden sites. Human-designed directories are prepared by subject experts who evaluate the quality of the information on these sites.
Subject organized directories are useful if you:
While there are more of these directories than you think, the titles listed below are generally regarded as the best ones available. They each have their own focus, so if one doesn't work for your particular topic, try another one.