Association of American Medical Colleges - http://www.aamc.org/
Provides information and links to the 125 accredited U.S. medical schools, 16 Canadian medical schools and 400 teaching hospitals and health systems.
Educational Testing Services - http://www.ets.org/
Provides a lot of information related to standardized testing. Includes information and practice questions for the GRE, GMAT, TOEFL, LSAT and teacher tests.
Graduate School Guide - http://www.graduateguide.com/
A comprehensive guide to Master's, Doctoral and Professional degree programs searchable by field of study and state.
Law School Admission Council - http://www.lsac.org/
Offers information on a variety of law school related programs including the LSAT, Law School Forums and database assembly services. Provides links to member schools and related world wide websites.
Peterson's Guides - http://www.petersons.com/graduate/
Provides wide-ranging information on graduate and professional programs offered by accredited colleges and universities in the U.S., Canada, Mexico, Europe and Africa.
Test Prep Resources site from the Penn State Libraries - http://guides.libraries.psu.edu/testprepresources
This site lists free resources, including practice tests and test prep books, to help you learn the skills necessary to succeed on commonly-used standardized tests. Select a test from the left sidebar.