Gentle introductions? Not really. The most gentle you're going to get would be how to use existing signal and slot mechanisms, like boost::signals, not rolling your own. The problem is that a general purpose signals and slots mechanism in C++ tends to somewhat involved since C++ doesn't exactly present a sane function reference model. Ex: the result of the ->* operator can't be stored.

A good source for learning how to roll your own would be the book Modern C++ Design. It goes into detail on how to make a generalized callback mechanism.

Try looking into Qt..I use it professionally and it works quite well.

http://www.trolltech.com/products/qt/