FFF is pretty rad, as is Slim framework. I like Slim so much I've been cloning it for Hack[0]. With the next week off work, I'm looking forward to getting it close to parity!
Cool. My personal preference is towards these leaner micro-frameworks in general. I've looked at Slim, seems cool, but never worked with it. Good luck on your project.
[0] https://github.com/LeanFramework/Lean