Don't know if this has been posted here already, but Cocos3D a 3D modeling space extension to Cocos2D has been announced. I have to buckle down and finish the game I'm working on at the moment but I'm really eager to take this for a spin!
I could have really done with this when I made Head Spin 3D. In the I had to roll my own 3D within Cocos2D. It's far from perfect but it worked in the end. If I ever need to do more 3d in the future this will make like so much easier.