The real hotbed for open source content management is sourceforge.net . While there is plenty to choose from, phpwebsite was the best fit for me.
This is actually an area I have thought about pretty hard, permit me to rave a little, based on experience at the coal face. The type of sites I am talking about are for engineers, manufacturers, agriculture, etc. Lets take a look at why small business websites fall over, fade out or never get built:
1. The perception that HTML is hard to learn.
2. No traffic due to no marketing. Most of these small businesses (1-10 person) do no real offline marketing, so why would they know how to market online.
3. Lousy content. No matter what you tell them as a designer, the content that you get will be "me" oriented. "Our business was established...." Even getting useable content will be like pulling teeth. Many times when asked for a logo I will be handed a business card and told to use that.
4. No updates or new content added.
5. No sales due to 2 3 & 4 above.

In my view web "designers" have done a great disservice to these type of customers. Lets face it, they do not really need "design" as such. Any reasonable template will give a good enough framework to display your content. What they do need is linkage, promotion, visibility and copy that at least attracts leads, better yet, actual sales. Most designers are "hit and run" thinking. Build the site, get it online and move on to the next site. The site gets 10 hits a month, by some fluke, and no sales. The owner quite rightly sees the web as a waste of advertising dollars and pulls the plug.

The next step? From my point of view, the next step is a total management system. I own the site, write the copy and promote it. The business pays only for results; leads or sales. From here you get to the point of creating your own hubs in specialised areas, leading to your sites becoming the natural point of contact for that industry. How does this all tie back to content management? One database can run several sites, all with different content. Combine RSS feeds for industry news. Well, I'm working towards it, but I'm not there yet.