Take a look at
e107 CMS . It very easy to set up and maintain, highly cutomizable and there are plug-ins for just about anything you can imagine.
It's completely php/mysql and free to use. My biggest complaint with it is they don't make it particularly easy to find what you're looking for when you visit thier site. Instead of having everything under one roof they have spread it out over several sites each of which you have to re-register with to access all of the information you need.