I am in the midst of a reorganization of this website. This week, I upgraded the forums to Vanilla, and I have been looking into a new Content Management System called ImmerseCMS (or icms).
from an end user standpoint, icms is a visually pleasing, intuitive, easy to use way to manage your content. The developer, Alex, has taken a lot of care to make use of unobtrusive JavaScript. It feels like when I am in the administration center (which is totally skinnable) I am right at home on a desktop app. It is well laid out, well thought out, and, for being young, very cohesive so far.
As a developer, the API has little to no documentation at this point, but if you know anything about OO PHP, then you should be able to look through the files in "/apps/icms/lib/front/" and you get a pretty good idea of how easy it is to develop for this framework. I am ok with doing some heavy lifting every once in a while, but its almost like Alex thought of everything I would want to do with a CMS before I knew I needed it?
Take a look at the plugin architecture to get a good idea at how powerful and well organized the API is! 
BTW, Alex also created Etomite, which is where MODx came from which is what is powering PirateMachine.org right now!
Download ImmerseCMS right now!
-sD-
Dr. Scotty Delicious, Scientist.