Joomla! is a good package for this, I have about 100 charities and organisations running their own websites. People up to the age of 82 using Joomla! to manage their own websites most of them would have little or no computer knowledge.

The most important factor in the whole thing is how much they know how to use a computer. If they don't know very much then I usually set up the website and write step by step exactly what they have to do to add content, add an image etc. And then anything more complicated they contact me.

If they have a bit more computer knowledge I let them a little deeper into the system to do whatever they are capable of doing.