This link came up in a forum. They give you a few weights and a beam balance. The challenge is to put the weights on the balance so as to balance it. (No Pun Intended)
Go and play the game, really.
Now that you've played the game, think of a way to program your way to a solution.
More specifically, the programming problem is this:
You will be given a set of integer such that there is a subset whose sum is exactly half of the sum of the set.
Identify that subset.