I have a huge amount of respect for Dries Buytaert, founder of the Drupal project (and potential new member of the Aquia team, which is a stealth-mode startup funded by North Bridge Venture Partners and focused on monetizing Drupal). When you've been involved in open source for a few years, you realize just how amazingly hard it is to create a project that can attract thousands of developers and tens of thousands of users.
Yet Dries has done just that. The thing I love most about Drupal is its Firefox-like plug-in community. Dries architected Drupal in such a way as to make add-ons easy and fun, and the result is that Drupal has a wide array of them. More importantly, he attracted a community that wanted to build these extensions.
In this PC World interview, he talks about how it came about, and ends up giving some great pointers on how to build a successful open-source project, including why he chose PHP (which I've covered before):
The Web is built by millions of individuals, many of whom are amateurs. They continuously update, tweak and rebuild their Web sites. Scripting languages like PHP lend themselves to that, and are widely available at affordable prices. It would have been very difficult to get critical mass if Drupal was written in a programming language like Java. Not because Java isn't as good a language, but simply because Java isn't as accessible as PHP.
So, while some have ignored PHP because of its amateur status (I remember introducing an entrepreneur to VCs and he was shot down because his code was PHP-based ("lightweight"), not Java or .Net), that is precisely what made Dries opt for it. He thinks differently, and his success shows the dividends that can come from such thinking.
Through it all, Dries recognizes that community, not software, is the first consideration in any open-source community. His attention to the Drupal community has made it into a premier open-source community. All while being a PhD student in Belgium. What did you do during your undergraduate/graduate studies? :-)