Sorry I've been out for a few days, but work duties call, and I must finish a small project. Nevertheless, I'm working on an article concerning building applications that support custom plugins. Of course, you'll be the first to know :)
p.s
Also, if you have any specific topics around this subject that you'd like me to concentrate on, feel free to drop me a line via the "contact" link. If it's feasible, I'll add the topic ..