Horus Framework
Smart Micro PHP Framework inspired by Sinatra in Ruby but not a clone
...Focused on a light codebase and on a solid, standards-friendly approach, Horus can be used to write advanced applications without having to deal with complex coding toolkits like Zend or CakePHP.
Horus is easy to learn and the code is pretty well commented in case developers need help figuring out what's going on.