Masyu, also known as Pearls, is an NP-complete logic puzzle created by the makers of Sudoku. Brandon McPhail provides a few free puzzles to get your feet wet on his web site (Java applet). Once you've mastered those, UCLICK Games offers a free daily puzzle (Flash) with the past month of archives available too. [more inside]
posted by The Winsome Parker Lewis on Jan 18, 2012 - 28 comments

Since 1980, Nikoli^{^} has been in the business of creating many different variations of logic puzzles (such as the very popular Sudoku and Kakuro). Unfortunately, as they're stationed in Tokyo, their magazine is unavailable to most Americans.

Luckily, over the decades they've inspired quite a few people to make their own puzzles and variants, including:

• The Art of Puzzles, by Thomas Snyder (updated weekly, plus bonuses)
• A Cleverly-Titled Logic Puzzle Blog, by Grant Fikes (updated several times a week)
• Melon's Puzzles, by Palmer Mebane (updated daily)
• Detuned Radio, by Tom Collyer (updated weekly)

posted by flatluigi on Feb 17, 2010 - 12 comments

We all love Sudoku, and we like to play it. But now there is KenKen, a new version that includes simple mathematical equations. [previously in MeFi]
posted by dov3 on Mar 27, 2009 - 39 comments

For those who tire of the usual paper and pencil-based puzzle, try Websudoku.
posted by Rothko on Nov 10, 2005 - 42 comments