@phpdeveloper.org
In this new post on the SitePoint PHP Blog, there's a look at the Wikipedia and Mediawiki software in the context of the PHP world.
That wikipedia runs LAMP makes it somewhat of a poster-child and, as you may know, the software used on wikipedia is mediawiki, written in PHP. Given the scale of the technical problem the wikimedia foundation has had to solve, what's been a little frustrating in the past finding detail from those involved on how they do it. Thanks to Brion Vibber we now have more information...
There's mention of Brion's talk presented to Google as well as the more recent Pro:PHP Podcast intervew with him detailing Wikimedia and PHP's place in it.