Subject Directories

Academic Info - gateway to college and research level Internet resources maintained by former librarian Mike Madin and a volunteer group of subject specialists
INFOMINE - large collection of scholarly Internet resources collectively maintained by several libraries, including those from the University of California
The Internet Public Library - large, selective collection maintained by students in various programs in information science
Intute - UK-based collection of resources for education and research, including collections in the sciences, social sciences and humanities
Librarians' Internet Index - carefully chosen, organized, and annotated directory maintained by a large group of librarians in California
Subject Guides A to Z - extensive collection of subject pages from the University of Delaware Library
The WWW Virtual Library - guides to many disciplines sponsored by the W3 Consortium

About.com - large collection of topical collections gathered by company-certified subject specialists
Google Directory - version of the Open Directory Project using the Google PageRank technology
JoeAnt - guide compiled by volunteers; each listing is accompanied by an information page that includes a site description, related JoAnt listings and keywords, and its Alexa ranking
Open Directory Project - significant resource collection compiled by thousands of volunteer editors owned by America Online and promising extensive expansion.
Yahoo! Directory - directory contained within the famous Yahoo! portal; lacks reliable site evaluation, so is not an appropriate source for academic research

These are archives of high-quality directories that are no longer being maintained.

BUBL Link - UK funded project of selective resources from the University of Strathclyde Library in Glasgow, Scotland
The Scout Report Archives - searchable database of 10,000+ critical summaries of Internet resources for the academic and research community included in the Scout Reports