Anatomy
www.bartleby.com/107 Full text and pictures of the classic Gray's "Anatomy of the Human Body"
Art
http://artchive.com Guide to online images of works by hundreds of prominent artists
Biology
www.biology.arizona.edu University of Arizona site, geared mostly to high schoolers
Chemistry
www.chemicalelements.com Of the many periodic tables of elements on the Web, this one's particularly well designed.
Geography
http://www.usgs.gov The USGS undertakes scientific research, monitoring, remote sensing, modeling, synthesis, and forecasting to address the effects of climate and land use change on the Nation’s resources.
Languages
http://translation.langenberg.com Nice selection of free translation engines
Literature
http://www.gutenberg.org Spectacular collection of 16,000 public domain books, including all of Shakespeare, "Moby Dick," "Aesop's Fables" and numerous religious texts.
www.sparknotes.com Mostly a commercial site, but it also has hundreds of free study guides to classic literature and drama
Math
www.webmath.com Several types of practice problems and the chance to e-mail an expert of help
www.algebrahelp.com Algebra practice problems
www.edu4kids.com/index.php?TB=2&page=12 Remember flashcards? here's an online version
Music
www.music.indiana.edu/music_resources Links to information on music eras and genres, composers and performers, from Indiana University
www.allmusic.com Large database of music types, history, and artists
Political Science
http://thomas.loc.gov Library of Congress site has updates on pending legislation and the daily Congressional Record
Reference
World Facts
www.cia.gov/cia/publications/factbook The CIA's public compendium of inofrmation on countries worldwide, including population, government, geography, agriculture, health systems, languages and broadcast stations