The eyeballing game: compare your best attempts at several instinctive everyday tasks - determining a point of convergence, bisecting an angle, finding the midpoint of a line - against mathematical certainty. In a more financial mood? Play Chartgame: given a random historical stock chart of an unnamed S&P 500 company, choose to buy and sell as time advances to see if you can beat the market.
posted by Bora Horza Gobuchul on Oct 14, 2009 - 22 comments

You have spacial skills. Apply them in Building Houses 2, on mathsnet.net. Or freestyle in Building Houses 1. Or at night! Oh and also there's like a hundred more puzzles over there too. Some java required.
posted by cortex on Apr 12, 2007 - 66 comments

PhET - Physics Education Technology offers this astoundingly large library of online physics simulations. Play orbital billiards. Land on a cheesy moon. Experiment with sound. Or try more advanced quantum physics simulators. Still bored? Try the "cutting edge" catagory. Here's the complete index. (Warnings: Frames, Flash, Javascript, Java applets, graphics, sound, quantum timesuck.)
posted by loquacious on Feb 3, 2007 - 7 comments

The Pianolina - an addictive flash game - is something like a cross between Pong and WolframTones. Brought to you by Grotrian, piano manufacturers since 1835, the pianolina visualizes musical notes as little squares that chime when they bounce against each other or against a wall. Its sophisticated interface lets you add chords, gravity, or start with the basic notes of well known compositions like Beethoven's "Für Elise".
posted by jann on Jun 16, 2006 - 21 comments

Friday Flash Fun, and other games from the educational entertaining Maths is Fun. Just don't tell the kids they're learning.
posted by kyleg on Sep 16, 2005 - 4 comments

The Paso Doble is an eerie little puzzle game, something like a De Chirico painting come to life.
Oh yeah, a new Mersenne prime was discovered today by a 20-yr old.
Both links courtesy of mathpuzzle.com
(will i ever beat joseph devincentis?!)
posted by vacapinta on Dec 6, 2001 - 12 comments