LittleBlissCMS

The LittleBlissCMS (LBCMS) is a lightweight CMS that uses Moxiecodes TinyMCE as an in-browser WYSIWYG editor, released under the GPL LBCMS is designed and maintained by Bliss Webhosting. Designed for easy integration into small to medium html websites that need to be updated by non technical users.
LBCMS is perfect for web designers who would like to allow their customers or users to manage the content on their sites (news, specials, and other blocks of text).

It manages the following:

Stores content generated by TinyMCE in the XML file

Retrieves content from the XML file
Outputs content to the page based on "sections"
Manages edit permissions on "sections" of content
Allows for the creation and deletion of "content managers"
Content managers can be assigned edit permissions to specific sections
Importantly it does NOT use an RDBMS...

You can put as much or as little content into the CMS as you like, pretty much this entire site is handled by LBCMS (except the structure), but it's perfectly reasonable to have just a paragraph, specific section or individual page managed by it.