Craig:

Heuristics are normally used to find a "good solution" to a NP-complete problems, i.e. problems that cannot be solved in polynomial time. A "good solution" usually means a solution that has an acceptable deviation from the optimal solution. Note that it is sometimes possible to get an idea (say 5%) of the maximum deviation without knowing what is the optimal solution.

I use heuristics all the time in financial applications (maximizing yield, segmentation of assets), manufacturing (best ways to use/cut resources), and robotics (detection of potential "problems" in dangerous envronments). The main reason I get the off-the-wall contract type is that I am pretty good in applying or designing heuritics and will often touch (and even write a good solution) problems that nobody else will touch. Most programmers don't use them because they deal with problems that have a simple (i.e. polynomial in the mathematical terms) solution.

Daniel