Coolmath Karen (a college calculus teacher who doesn't reveal her last name) has created a network of sites for kids, parents, and teachers, dedicated to the proposition that math is fun. Enter the Kids! portal for math games, fun lessons and educational calculators for elementary and middle-school students. My favorite clicks are the interactive exhibits in Cool Things (don't miss The Splash) and the useful calculators (such as wind chill factor, dog years, savings and sales tax) in Calculate Stuff.
"When you back up from a small wall mirror, do you see more of yourself?" Figure This! is chock full of eighty printable math challenges and answer sheets for middle schoolers. You can use the challenges online by scanning the Challenge Index or Math Index for intriguing topics, or download them in batches in PDF format for printing and offline use. Parents and teachers will find tips on using the challenges in Family Corner and Teacher Corner, respectively.
Seventeen original games based on baseball, soccer, car racing and other fun things will intrigue even the most stubborn elementary-age math students. My favorites included Cookie Dough (learn to spell numbers up to 10,000 and don't forget that compound numbers from twenty-one to ninety-nine use a dash), Change Maker (in four different currencies) and Tic-Tac-Toe Squares (not your usual Tic-Tac-Toe.) Some of the game pages were a little slow to load, but the quality of the games overshadowed this one drawback.
Teacher and mom Wendy Petti created Math Cats to promote "playful explorations of important math concepts" for elementary and middle-school students and she's certainly succeeded! I loved the interaction between math and art (see Math Crafts and Art Gallery) and the Micro Worlds activities. To get started, you will need to download the free Micro Worlds Web Player but it's worth the effort. Just look at the activity screenshots if need further convincing. To find activities for a particular age, click on Site Map and Info.
Fun Facts from the mathematics department of Harvey Mudd College are tidbits designed to arouse mathematical "curiosity and fascination" and to show high-school and college students that there is more to math than calculus. Facts can be read randomly, or queried by subject (such as algebra, geometry or probability) and difficulty level. You can even submit your own fun fact for possible publication. For an example of one of the easiest facts, look up Mind-Reading Number Trick in the search box.