Puzzles with polyhedra and numbers. In this
site one can print copies of polyhedron puzzles (for non-commercial
purposes only) and one can read several mathematical articles on the
subject.

Steven H. Cullinane is semi-retired from work as a systems
analyst/programmer. His interests are chiefly mathematical and literary. The site highlights his
Diamond theory and
the Diamond 16
Puzzle, based on it. Also you'll find there some other topics related with mathematics.

Science U: for people who like science. A
kind of virtual science center with Geometry Center, Library,
Observatory, Studio, Info Center, and even a Store. Browse through the
articles, puzzles, instructions and multimedia that will help you to
learn as much as you wish. Science experience!

Welcome to the marvels of mathematics with
Ivars Peterson! This prominent mathematician, a member of The
Mathematical Association of America will guide you through many
amusements of the math world. His other contributions to MAA Online
include the
Math
Muse for Kids column.

It's all about three fields: magic squares, magic stars (mostly original material) and miscellaneous number patterns. It can be useful to anyone interested in recreational mathematics. Moreover site is created to be understandable regardless of your education level.

Martin Gardner said that no other person in the World knows more about geometric dissections than Greg
Frederickson. Just explore Greg's unique book, Dissections: Plane & Fancy, published by Cambridge University
Press in 1997, and you'll understand why.

At the site you'll
find a collection of knots, mostly viewed from a mathematical
perspective. To create, visualize and manipulate mathematical
knots in three and four dimensions you can download and try on
your computer an elaborate program - KnotPlot.

Blet is developed by Fernando Rodriguez Villegas from University of Texas at Austin, Texas, and his colleagues. The objective is to maximize the number of 1's clicking in the middle of triple patterns like 010 or 101.

A huge collection of mathematical puzzles and
puzzling mathematics. With more than 200 Java applets, this is one of the most
interactive sites one the Web. You may spend many pleasant hours at this site.

Ed Pegg Jr. and his weekly site contains
pretty clear and funny puzzle collection, great high level discussion, and
modern geometric and spatial novelties from all around the World.