These search engines act as clearinghouses on a wide array of specific subjects. They usually consist of guides compiled by subject experts on relevant resources to particular topics. The following are some of the clearinghouses that can help you retrieve relevant information:

The Argus Clearinghouse features 13 main categories, such as information technology, education, government and law, social science, etc., divided in sub-categories that lead you to information related to particular topics.

The WWW Virtual Library is also organized by subjects. The information provided on a particular topic includes bibliographies, Web sites, listservs, and research papers.