If you've been looking for a great way to start branching out into the Model-View-Controller world of PHP frameworks, but have been intimidated by the learning curve of some of the others, you might consider CodeIgniter. The Lear-CodeIgniter.com site has that can help you get started down your road to understanding it.
This is our first episode in our CodeIgniter Basics training series. This episode explains to you what CI is, what MVC is, and the overall structure of CI, as well as a standard install. Enjoy!