Numbat
Numbat is a really, really small CMS where items are identified by one thing only... their URL. It is also completely media independent, as you can use the view system to create almost any type.
Numbat also features a built-in administration, but it is extremely light by design.
Downloading
You can download a zip archive or tarball.
The source can be obtained from GitHub by forking it:
$ git clone git://github.com/rmccue/Numbat.git