Links to resources that are not easily searchable from general search tools such as Alta Vista and Hotbot. Listing includes links to medical clinical trials, FDA Orange Book for drug products, nuclear explosion database, corporate grantmakers and private foundations. This is the expanded outline of the Encyclopaedia Britannica. EB editors have hand-picked the best sites for over 140 topics. Unlike the subject trees, there is no human element to match your subject with sites.
Search engines offer more options than simply following links in a subject tree.
Check the front page for 'advanced' or 'customized' searching. This page will usually give you more options to refine your search. AltaVista Massive and fast indexer of full text, updated daily. Otherwise, AltaVista will find every instance of each individual word. AltaVista indexes both the Web and the last two weeks of Usenet newsgroups.