I’ve been subscribing to Science News since 1995. [As I get older, Science (and Religion) become more fascinating.] It’s an excellent weekly news magazine of science, usually about 16 pages with minimal ads and concise (1-2 page), up to date articles. One of the features of Science News is an occasional column (blog) written by Ivars Peterson, called Math Trek Blog.
Mr. Peterson has written several articles about Sudoku for the magazine, notably:
Sudoku Math (June 2005),
First World Sudoku Championsip (March 10-11, 2006),
Pentomino Sudoku (May 2006) and
Sudoku Class (February 2007).
His articles focus on aspects of Sudoku in a clear, concise way and unlike other (opinion) columns, provide a bibliography to other sources of information. His latest, entitled Sudoku Class, provides information about Sudoku in classrooms, Math conferences and describes a Website by Dr. Laura Taalman (of James Madison University) called Brainfreeze Puzzles.
Although not updated in 10 months, Dr. Taalman’s site describes eleven Sudoku variants with examples. She is co-authoring (with Philip Riley) a new book called: Color Sudoku to be published in May 2007, containing examples of these variants. (Perhaps that is the reason for the frozenness [no pun intended] of her website.)
On her University website, Dr. Taalman conducted and preserved a Sudoku Puzzle Problem of the Week contest from January through April 2006. Thirteen downloadable Sudoku variant puzzles (with solutions also available) are shown there. I haven’t tried them yet but plan to.