Morpion Solitaire is a very simple pencil-and-paper, line-drawing game for which the best possible score is not known! New records are still being set.
posted by Wolfdog on Jan 8, 2012 - 21 comments

   MEFI
   META
+ ASKME
-------
 FILTER

Each letter corresponds to a number 0-9. The solution is unique. [more inside]
posted by Upton O'Good on Sep 3, 2008 - 27 comments

Fun and games with mathematics and mathematical puzzles (e.g. heart basket, Rubik's Cube, Rubik's Magic, hypercubes, and more) in both English and (with yet more content in) German.
posted by Blazecock Pileon on Feb 18, 2008 - 6 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

Who has the fish? Einstein logic puzzle. If I can do it, you guys can.
posted by swift on Aug 4, 2005 - 53 comments

64=65? there must be some kind of trick to this, right?
posted by pyramid termite on Aug 18, 2004 - 30 comments

"WARNING!!! The puzzles on this site are very difficult, and most require the use of a good spreadsheet program in order to solve them. It will take many hours, perhaps days, to solve each puzzle..."
posted by limitedpie on Aug 11, 2004 - 7 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