You can add these puzzles to your iGoogle homepage by clicking the button below:
There are currently over 1200 puzzles on this site. Every puzzle has a single valid solution I think some of the puzzles, particularly the larger ones, may be a bit too difficult, but I suppose you'll have to determine that for yourself.
Are these KenKen puzzles? Technically, no. KenKen is a registered trademark, and the people behind it clearly intend to create a Sudoku-like frenzy for such puzzles, and then collect rents on their trademark. Therefore, I wish to make clear that I am, and my solver and puzzles are, in no way associated with official KenKen-brand products. That said, these puzzles can be solved with exactly the same techniques one would use to solve KenKen puzzles.
Incidentally, I have written a solver for KenKen puzzles. It's not needed for these, of course, since they come with built-in solutions, but you might find it useful for other, paper-based puzzles.