I had the pleaure of answering some questions for Sam Turri of GOODSIR awhile ago. This has been on the web but I haven't linked to it yet. There's a lot of great information about PortlandLabs and Concrete5, as well as a profile of me, Franz and some active community members.
THE CONCRETE5 CMS: POWERFUL AND EASY TO USE
If you're looking for an open-source CMS with sensible, easy-to-learn administrative tools and the power to house powerful applications, concrete5 should be your first choice. At GOODSIR concrete5 is our preferred web platform so we went to the source and asked the concrete5 developer community to help us explain why it’ll work so well for you.