Non-linear Optimization anyone?

[lightw1thoutheat]

anyone know of a good site dealing with non-linear optimization. i have a good understanding of linear optimization, zero sum games, and fairly solid grasp of general sum games (just finished reading most of nash's phd thesis). It's not the math that scares me, i just cant seem to get my head around some of these issues.

The problem i see is that you can't use the lagrange mulitplier theorem in non linear cases easily.

ideas?
thanks
-light