Ralph Schindler has a new post to his today looking back at a sort of history of autoloading and some of what we've learned even in just the journey from PHP 5.0 to 5.3 (and has become best practice in the community).
It wasn’t until years later that certain best practices had emerged and the prolific usage of require_once/include_once throughout large bodies of code had started drying up. Even after autoloading had been adopted by larger more visible projects, a common patten had yet to emerge. [...] Fast-forward to today, and we see that this standard for autoloading has agreed upon by a large number of projects and has come to be named the "PSR-0 autoloading standard".
He covers some of the things we (the development community) have learned about autoloading and resources in our applications. He talks about the classmap tool that Matthew Weier O'Phinney developed (and some of its downfalls) as well as a move into PHP namespacing that has helped to make some of the "namespacing" based on class names obsolete. He's noticed a pattern in namespacing already - a self-contained structure that provides more of a "drop in" solution and how that's handled in the code.