92 years young, the delightful Raymond Smullyan is a mathematician, logician, magician, concert pianist, and Taoist philosopher - who also pioneered retrograde chess problems.
posted by Trurl on Jun 26, 2011 - 22 comments

DroidQuest, Gate and Logicly are modern logic puzzle games based on the classic educational games Rocky's Boots (1982) and Robot Odyssey (1984). [more inside]
posted by speicus on Nov 2, 2009 - 22 comments

A virtually unlimited supply of randomly-generated logic puzzles, in a variety of sizes and difficulties: Nonograms. Slither Link. Nurikabe. Bridges. Light Up.
posted by Upton O'Good on Nov 28, 2007 - 18 comments

Arghhhhh!!! Aghhhhhhhh! Arghhhhhhh!!!

Cheats for PuzzleDonkey4 Available here
posted by willnot on Dec 1, 2004 - 55 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