Code
barebonesmvc-php
BareBones: a one-file, no-configuration, MVC framework for PHP5.
Update: "Re-branded as jackrabbitmvc as of June 2013" and self-hosted as a fossil repository; see: http://use.jackrabbitmvc.com
NOTE: Now with routing, and the ability to write response without specifying view file (e.g. XHR responses)