Make member functions into free-standing friends. [Restrictions apply]

Anytime someone asks about member function pointers, I feel obliged to post this article about C++ delegates. Basically, it's exactly what the OP is looking for with a very convenient syntax, and totally cross-platform.

Of course, the article is mostly a discussion about why the problem is so hard, and it gets pretty technical... but he also gives his solution, which is the coolest thing evar.