I favour Kohana ( http://kohanaframework.org/ ). Very quick and easy to get the core of your app built. Only (and potentially major) downside is that the documentation can be tricky to wade through. I'd run away from CakePHP. Caveat: last version I worked with was 1.3. The weird way it uses arrays in its ORM to kinda-sorta-but-not-quite work on the database always hurts my head. In fact, the whole way of going about…
Kohana's tutorials are pretty bad, but the API browser is solid and the code of the framework itself is very readable.
As a beginner, having to dig under the hood of Kohana to fully understand it initially turned me off, but I came away with a much better understanding of how MVC frameworks work.