This PHP framework is probably one of the easiest frameworks to get your head around. It was released a couple of days ago and it has been real impressive. Though relatively new it has a lot of the standard features while offering new stuff like Image Manipulation, Email Class, Encryption, Benchmarking etc. The best part about it is the low learning curve. As part of an experiment I recoded the entire CougarCS library with it and it was quite a pleasant experience.
Replacing the library with this code is another issue, but it was done real quick
Have a go at it here ==> CodeIgniter