Sources of Kakuro Puzzles
Here are some great sources for Kakuro and Kakuro-like puzzles. If you have any suggest, please send them along to support@kakurocalc.com.
YouPlay.com (requires Flash)
YouPlay.com boasts numerous puzzles, including Kakuro, Sudoku, and variations of the two. Five new puzzles of each type are provided every day.
Puzzles are free. You may play them as a guest, or get a free membership, which allows you to see any high scores you may acheive appear on the leaderboard.
For a fee, you can get access to archived puzzles and compete for cash prizes. The site is in Australia; cash prizes are not available in the United States.

Kakuro at YouPlay.com
If you like Kakuro, check out Adduko. It's like Sudoku, but instead of starting with some squares filled in, the board is broken into sequences of squares--you're given the sums of the sequences, and use Kakuro-like logic to determine the sums and fill in the board.
CALcuro is like Kakuro, with two big differences. First, the clues involve not just addition, but subtraction, multiplication and division as well. Second, a sequence may contain more than one occurence of the same digit.
Clues are not automatically provided. The Hint button will fill in a square each time it's hit. KakuroCalc may be useful when playing Kakuro, Adduko, and (depending on the particular clue) CALkuro.
Here's a helpful hint for YouPlay: if you look at the leaderboards, you may be amazed at how high the scores are, and out the miniscule time it takes the leaders to get those high scores. The scores are somewhat meaningless, because there is a trick to running up your score.
Here's how it works: you get points at the moment you complete a sequence. The number of points depends on how much time has passed since you last scored points. The secret is to complete sequences in as short a period as possible. People with really high scores often find themselves with the board nearly filled-in, but with zero points. At that point, each square they fill in completes a sequence and they rack up the points.
Daily updates providing numerous puzzles of varying difficulty make YouPlay a real bargain. The fact that the puzzles are available for free are icing on the cake.
ConceptisPuzzles.com (requires Flash)
ConceptisPuzzles.com provides Kakuro, Sudoku and several similar puzzles, as well as some amazing graphic puzzles, including the crowd-pleaser Pic-a-Pix. (If you like Pic-a-Pix be sure to check out Sym-a-Pix).
All puzzles are updated on Fridays, with about six-to-ten puzzles of each type. One puzzle of each type is free. The rest may be bought using points purchased from Conceptis. 500 points cost $6US. The number of points required to purchase a puzzle varies from puzzle to puzzle and from type to type. Number puzzles tend to require fewer points than graphic puzzles. A Kakuro puzzle typically costs 4-15 points.
250 points will buy all of the puzzles of the week.
Once you have bought a puzzle, you may save it indefinitely and even replay the puzzle.

Kakuro at ConceptisPuzzles.com
Conceptis' number puzzles provide an automatic hint system. If you hover over an area of the board, you can see a display of all possible number combinations that might fit into that area. The display sometimes truncates the list of possibilities; in these cases, KakuroCalc might prove useful. Most of the time, however, you'll already see all of the possible sums.
CalcuDoku is a Kakuro-like puzzle that may involve addition, multiplication, subraction and division. Unlike YouPlay's CALkuro, each puzzle has a list of operators it will involve. Some may involve only addition or multiplication, some may involve two operators and some may involve all four. Not surprisingly, multiplication-only seems to be the easiest and addition-only the hardest.
Unlike Kakuro sequences, a CalcuDoku sequence may contain multiple occurrences of the same digits.
Although updates are only weekly, and most puzzles cost a few pennies, ConceptisPuzzles.com provides a large variety of puzzles that are both interesting and challenging and well worth the price.

