Insight Personality - Sometimes when you try to classify people according to certain traits, that classification is entirely arbitrary. This online personality test is the best I've found, because it defines personality as a hierarchy of traits. Check it out.
Nova's Poetry Haven - From the author of Psych_Girl's psychology comes her personal poetry site, complete with original poetry, submissions from other, and guidelines to writing your own poetry. Submissions from the public encouraged.
Psych_girl's Psychology - High school student's site devoted to psychology and psychoanalysis, with sections on behavior, biological aspects of psychology, Freud, phobias, etc.
Thinker's Domain - My personal site about biology, anthropology, astronomy, and organic chemistry. I also have cool interactive games like "Lost in the Desert" about desert survival and "Choose Your Own Adventure: African Safari".
Tripod Fun & Games: Daily Crossword - Exactly what it says. The homepage headquarters offers a Java crossword puzzle every day, and an archive of past puzzles.
Welcome to Mad Trivia! - Twisted trivia site where you can win $$$ if you know the right answers. 10-12 new questions daily in a themed topic.
ChemFinder - An excellent site for information about almost any particular compound, including physical properties, and often pictures and links. (June 3, 1999)
Organic Reaction Quizzes and Summaries - This site has reactions grouped by functional group. Includes reagents and explanations. Par excellence for organic chemistry students everywhere. (June 3, 1999)
Periodic TablETRIS - This is a Shockwave game, inspired by Tetris, to practice learning the location of elements on the periodic table. Demo on site, and you can always buy the full game. (June 3, 1999)