I was asking around for a plugin / library / component / *something* that can help me to easily integrate the use of PayPal into the CakePHP application I'm building to be the web site for my upcoming book. One of the movers and shakers in the CakePHP community, (you know, those people who actually contribute some code) John Anderson (aka psychic, the lead on the CakePHP Cookbook project) mentioned that he had a plugin I could use. He also provided a link to an experimental CakePHP plugin server he's setup and asked people to play around with. That PayPal plugin was one of the ones being offered.
Basically, you download a CakePHP console application that John wrote which speaks to the plugin server, and then it allows you to install any of the plugins that are on the server. Perhaps the first steps towards a number of plugin servers?