National Council of Teachers of Mathematics
The Math Forum: Polyhedra in the Classroom
Lesson plans for many student activities which introduce the concept of polyhedra into the classroom. Some activities can be accomplished by hand with paper, pencils, and scissors, but the unit works best if the students can regularly...
Wolfram Research
Wolfram Math World: Recreational Mathematics
Recreational Mathematics contains lots of fun links to Mathematical Art, Number Guessing, Puzzles, Cryptograms, and seven other fun topics. Each area is explored in depth and is appropriate for both students and teachers.