I’m working on a new CMS called 900dpi that’s very simple for clients to use. Basically it just shows them the website and they can click on editable regions (defined with a CSS tag) to change content. It is automatically hosted on our site, and pulls files in through dropbox. We’re in private beta right now, but if you want an invite you can email me at abby(at)900dpi. It may be a good product for your clients.