CMSs are beautiful things. Just as CSS allows us to abstract the design away from the markup, a CMS allows us to use a database to abstract the content away from the markup. There are a zillion of them, each with different backend UI's and different ways to doing things.
But CMSs are for web people. Even my beloved WordPress can be challenging to train/explain to someone who has no experience working with websites. Perhaps this is the motivation toward a new trend in CMSs I'm calling "light" CMSs. Each of them attempt to make the task of updating content on a website easier and more intuitive. This is largely at the cost of features. These are for simple, otherwise static websites where updating content is the name of the game.
Unify is the dead-simple, in-browser content editor that anyone can use. No CMS, no database, no backend interface, no proprietary tags or syntax. Just you, your website, and your browser.
Unify is still in private beta, but it sounds like it's going well and should be out soon. Unify left Beta in August 2009, and as of March 2010, version 1.2.6 is in development.
You simply apply class names to block level elements you wish to be editable. You log into Unify directly on the website you wish to edit. You then are looking directly at the website again, but can click on the editable parts to bring up an inline editor to edit the content and save it. Publishing then literally rewrites that file and makes the changes live.
Finally, a free and truly simple CMS
I'm not 100% sure but I think CushyCMS might have been the first player in this market. They have been around a while, anyway. The theory is similar to Unify in that you apply a special class name to blocks of content you intend to be editable. You then set up an account at the CushyCMS website, provide FTP details for your site, and add the editable pages. Anyone with access to that account can then edit the content on that site. It's free, which is awesome, and has a premium component for branding it.
PageLime is a hosted Content Management System (CMS) for designers, web agencies, and web developers. It allows you to manage text, images, and documents on your site by logging into a web-app that's hosted on our servers. The best part is that it doesn't matter where your site is hosted, it doesn't matter whether you use PHP, Java, or ASP (or no scripting platform), and you don't have to make a single change to your site architecture.
PageLime is a combo of CushyCMS and Unify. It's like CushyCMS in that you have an account on it that you provide FTP details and give your pages editable classes (although you can add multiple websites to a single account). It's like Unify in that it has a live page preview with clickable editable regions and save/publishing. PageLime is a free public beta.
Perch is a really little content management system for when you (or your clients) need to edit content without the hassle of setting up a big CMS.
Perch is a PHP based system, which does use a database, but is otherwise just as easy to set up as the others. Instead of applying class names to editable content, you make the editable content special PHP functions provided by the Perch class. Logging into the backend gives you access to edit these specific regions. Perch is completely self hosted and brandable, meaning it will work for life and no third parties are ever involved again.