Population Research Institute: Web site
When I first started working with the Population Research Institute, their website relied on a proprietary content management system. Their site offered hundreds of articles, but they were full of hard-coded formatting like fonts, heading sizes, and colors (such as purple). Many hours of Perl and proofreading later, PRI had a new Joomla site with a clean, consistent look.
Joomla served them well, but fortunately, by the time they discovered the real constraints, I had discovered Drupal. Today, I rarely have to say, "Your site can't do that." In fact, I'd probably never have to say it, if I wasn't also responsible for ongoing site maintenance and security. I won't just slap any old module up; I need to be reasonably sure it's got enough other eyes on it to stay secure and maintained.
By the way, I can't take credit for the sleek design you see pictured -- I get mockups from PRI's in-house designers (one of whom is my brother) and translate them into CSS and Drupal.

