You shouldn't use ResourceForks for *your* application. However, I'm planning on making a nice wrapper for ResourceForks using the Resource Manager Carbon calls...
Most Carbon is straight C, though, so you can just call it from your Cocoa code. The Apple example is for C++ mainly, but I don't think there anything in Carbon that you can't do with C (although most people use C++ because it's easier to think about - OOP and so on

).