I've used a number of CMS's over the years.
The 2 most prevalent:
Expression Engine is pretty damn powerful but can be cumbersome when it comes to customizing it. Has plenty of addons and fairly good support [
http://www.pmachine.com]
Joomla which I just got turned onto over Expression Engine is a powerful and popular CMS that's super easy to customize and maintain. Has plenty of addons too..
Im now torn as to which one I would use if I had a gun to my head though.
As far as boards, Invision Power Board is one of my my favorites. Doesn't intergrate into either CMS though.
HTH