I've had the good fortune of building the last two versions of The Barbarian Group's website. Client work is fun, and full of creative opportunities, but no one "gets" you like your own team. Building sites that your friends and colleagues will see and use daily is awfully rewarding.
The most recent version is the best, naturally. We kicked it off in mid-2008, and I was involved throughout. We built it from the ground-up, with a Rails-powered CMS to manage all the site's content, including individual employee blogs and profiles, a comprehensive portfolio, timelines - even a counter of how many shoes the company owns as a whole. I also built a number of interal project management tools, which no longer exist.
I also built the previous version (last screenshot on the left), which featured - in keeping with our priorities at the time - a Flash front-end, powered by a PHP-to-XML system that I built.