Is there a CMS (Content Management System) that has no PHP or external database (such as MySQL)?
Is there a CMS that doesn't have PHP?
Clarifications due to comments:
requiring no other server-side language, such as C#, ruby, JAVA* -
Is file-based storage, such as sqlite acceptable?
Yes, as long as PHP isn't needed to access it.
or locally on your machine + uploading the HTML files
No, this would basically take away the need for a CMS.
Do you need a Web interface (for logging in, editing content, creating new pages, etc.)
What content should be managed?
Text and images.
Is a "fancy WYSIWYG editor" needed
No, HTML is fine.
Just to clarify a bit more: I'm running a test on using Dropbox to host a website. Right now I can only use static HTML files on it, as there is no "server side", so PHP pages can't run, there is no MySQL database handy on the localhost, which all means the 100% of all the CMSs I know cannot function in these circumstances. So the next phase in the test is to find a way to manage content via an interface, instead of just using static HTML.