Archimedes-lab.org is a free and collaborative edutainment project developed and maintained by Gianni A. Sarcone and Marie-Jo Waeber, two authors and writers with more than thirty years of experience in the fields of visual thinking and education.
The main goal of the web site is to teach mathematics differently and to make it accessible to everyone through visual puzzles and games.
The site walks visitors through various problem solving strategies and discoveries in the world of recreational mathematics.
Archimedes-lab.org is divided into four main categories: puzzles & tests, illusions & paradoxes, mind & brain, oddities & curiosities.
Here's a quote from Scientific American (May 27, 2003): "This virtual lab borrows the empirical spirit and creative curiosity that Archimedes brought to his work and invites visitors to explore with the same expectations for mind-blowing discovery."