I personally don't use any frameworks, I find them unnecessary and 90% of the time unnecessarily abstracted. I have some experience in Cake which seemed OK as far as frameworks go.

Since you're still relatively new to PHP (unless I'm mistaken) I'd strongly suggest you stay away from frameworks. While frameworks can make stuff easier they take away from learning how its done which is important to know. If you just want to screw aroun with them, Cake, Zend and Codeigniter are popular.