For those of you who don't know, this is the awesomest brain challenge ever! I found a book of puzzles today at WalMart and thought even though it seemed ridiculous, it was worth a try because I was really bored, and I figured if I didn't like it I could just toss the booklet since it was only a dollar.
It rocks! I have done two of the easy puzzles out of the booklet, and two from http://www.websudoku.com/ on easy mode. My fastest time with those was almost 20 minutes, these puzzles are definitely a challenge! And for those who want to try it but don't know the rules, here's the lowdown.
You get a nine-by-nine grid with some numbers in some of the boxes. Each of the nine-by-nine grids is made up of 9 three-by-three grids. Each little grid should be filled in (by the time you finish) with the numbers 1-9. The challenge? You cannot repeat any number in any row, grid, or column. Oh my god it's tricky. But I like it, and can't wait till I feel comfy enough to do some of the more challenging ones, LOL ...
For simpler rules, check out http://www.conceptispuzzles.com/products/sudoku/rules.htm
Seriously, everyone should try this!