Biographies of Famous Mathematicians
Flatland: A Romance of Many Dimensions
Math Quotes
The Mozart Effect
Trebuchet (try your skills with a trebuchet here)
Fractals
M.C. Escher
U.S. Naval Observatory
Fibonacci Numbers and Golden Ratio
Math Puzzles and Games
Geothermal Heating
Math in the Movies
2 Different Free IQ tests based on patterns and iterations:
http://www.iqtest.dk/main.swf
http://similarminds.com/intdoor.html