Smath
Several years ago, the Smath board game caught my eye and I was lucky enough to be able to purchase it at the time. While I haven't used it with the kids as much as I'd like, that's no fault of the game's! Smath is an excellent math teaching tool, that I wish I could get my children interested in a little more often.
Set up along the lines of Scrabble, the object of the game is to use your number and math operation tiles to create math equations, building off of the other players' works like a crossword puzzle. All of the tiles (except equal signs and brackets) have a point value, and there are various 2X and 3X bonus spots along the board.
You get a game board, storage bag for the tiles, four tile racks for gameplay, 6 each of the numbers 1 - 12, 10 blank wild tiles, 36 equal sign tiles, 9 each of the four operations and 24 bracket tiles (parens). You'll need to break apart all of the tiles, as they come attached to each other like pieces of a model car.
Gameplay can be as simple or complicated as you like. Put all the equal signs in a community pile, along with the brackets, if they are going to be used. All the other tiles go in the bag, and everyone draws ten tiles to place on his or her rack. If your children are not able to use certain operations yet, simply don't put those signs into the game bag until they're old enough.
Players then take turns trying to make math equations on the board, and of course, the longer your equation, the better. Some examples given are:
5=5
2+3 = 5
12 - 7 = 5
1 + 5 = 2 x 3 = 12 - 6
(11 - 3) ÷ 2 = 2 x 2 + 0
Bracket tiles simply sit on top of number squares, because they're clear, and do not take up space on the board. Bracket tiles can also be added on top of numbers already played, when you are building on a previous entry on the board. There are also a number of blank tiles provided to be used as wilds, and can be used for any number or operation. The only problem with them is trying to remember what they stand for, as that's often less obvious than a blank in Scrabble.
Each player adds up the points listed on their used tiles, multiplies by any bonus squares he or she played on, and then posts their score. The game ends when all tiles have been played, or there are no other moves possible.
Smath is an excellent reinforcement tool for going back over the math concepts that your children are learning, and since you can customize the game by only using the operation signs that they know (or really need some extra work on) then it's not too frustrating. If your children like board games, and don't mind one that's "aw, math?!," this is a great way of increasing basic skills with yet more repetitious worksheets. You should be able to find it for around $15 or so. Enjoy!