Medicine - Links to medicine and 9 other major subjects are available from this site. Medical Matrix - Large, comprehensive and worth a bookmark. Registration is required, but it is free. MedNETS - This site is a relative newcomer. There are sections for patient education, CME, journals and more.
Registration is required in order to log on, but it is free.
Webplaces - My favorite directory. Lists all the major individual search engines and indexes worldwide. The World Wide Web Virtual Library - A directory of global Web resources arranged by subject categories. One of the most interesting developments in Web searching over the past 18 months. Searchable by keyword, retrievals will be shown by their size.