I mastered a little about Rails internals by looking at the source code (of the framework), changing some methods (and entire classes) sometimes and by reading

I mastered a little about Rails internals by looking at the source code (of the framework), changing some methods (and entire classes) sometimes and by reading the development mailing list, I recommend the same way of learning for everyone working with Rails. Anyway, it would be nice to have an article describing the changes Rails 3 will bring to this architecture.