infoplease.com
A combination dictionary, encyclopedia, and almanac useful for finding quick answers to general questions.
CNN Daily Almanac
Lists global events, current as well as historical, based on today's date. Upcoming events are also listed, and there is an archive that goes back to 1996.
PubList.com, The Internet Directory of Publications This is a fairly useful resource for locating basic information about magazines and journals. Note: it is useful for finding journal titles by subject, not specific articles in individual journals.
United States Codes
This site from Cornell University contains the searchable text of all the U.S. Codes. Alternatively, the text of individual code sections may be downloaded from the Office of the Law Revision Counsel.
United States Government Manual
This is the online version of the US Government Manual, with available versions going back to 1995-96.
LSAC.org The official LSAT (law school aptitude test) site of the Law School Admission Council (LSAC). One may use this site to register for the test online.
Medical Student Resource Guide Though highly commercial and of questionable authority, this site has some useful sections on test preparation and study skills.