"Virtual Hospital" -- Martindale's Health Science Guide to the Internet,
developed and maintained by Jim Martindale in association with the
library at the University of California, Irvine
The Medical Matrix -- Extensive
listing of medical resources on the Internet. A project of the American
Medical Informatics Association, hosted by the University of Kansas
Medical Library. Undoubtedly the best of the Internet medical directories
for healthcare professionals.
AltaVista -- The fast, robust
Digital Equipment Corp search system.
Excite -- One of the newer search engines that claims to search by keyword and concept. Seems to do pretty well.