In a new post to his blog Jonathan Street looks at plugins, specifically for PHP frameworks.
As far as I can see there is nothing stunningly new about [the django-monetize plugin] but at the same time I can see how it would speed up development. It's a good simple wheel that should save you from reinventing a wheel for each project you work on. This got me thinking about php frameworks.
He mentions the Zend Framework, CakePHP and Solar as examples of where plugins could be some of the most effective. He stretches it to even say that applications like Magento and wildflower could be considered "plugins" for the Zend Framework, enhancing its functionality beyond just the framework.