One of my favorite booths at Toy Fair this year was Thinkfun. They make a wide array of puzzle games with multiple games for each age group. I spent nearly half an hour talking to the founders of the company and was genuinely impressed. They are actually passionate about the games they design and spend a lot of time play testing them to ensure their success.
In the end they gave me three games to test out, two of which we played for a while in the hotel bar after dinner one night. The one that surprised me most is Math Dice. The premise is simple and I thought it might be too difficult, but as a casual game it really works. We started out slightly competitive, but soon found that a collaborative effort was both easier and more fun.
The rules are simple, and most geeks should have the required dice on hand. To start, roll 2d12 and multiply the values, giving you a number between 1 and 144. Next roll 3d6 and try to find an equation using those numbers that comes as close as possible to the target number. For example if you roll a 9 and 4 your target number is 36. If the 3d6 roll as 3, 4 and 2, then a possible equation could be 3 * 4 * 2 for 24. You can also use powers and roots, so the best answer would be 3^2 * 4 = 36.
If the round proved too difficult, or impossible, then we’d just re-roll and keep going. No score was kept and no egos were bruised.
For more in depth rules, including tournament play, check out the Math Dice site. In addition to information about the game they even have a series of Flash games that you can play online.
If you don’t have any d12s, you can buy the Math Dice game, complete with a rules pamphlet at Amazon for about $6.