2nd Sentry. Not exactly a CMS, but it allows the editing of content within any stack. It’s simple but really powerful. I\s say it’s in use, in either a big or small way, on almost all my sites.
The only real drawback to it (and it’s as much as feature as a drawback) is it uses a “flat database”, I think is the term. In that, there is no database to setup, all updates are stored within the stack files on the server. I say this is a minor drawback as a couple of times I’ve been caught out by my fondness for clearing out the server entirely and re-publishing entire sites, but forgetting to save the Sentry files on the server beforehand. Result… All edited content is lost!
Sentry is a “lite” version of Cotent in Armadillo (both stacks originally developed by the same person). Armadillo has the exact same feature, called “Content”, but the contents are stored in a database.
But ya, Sentry is brilliant.