I received a comment about another great tool known as CocoShop. What sets CocoShop apart is that it is fully open source so you can see how the tool was developed, and maybe even use it as a basis for your own tool (be sure to understand the license).
It is a very good and evolving tool, and is extremely useful for laying out GUIs, and can be used for creating scenes. This isn’t a game builder, but a time saving tool helping you place Cocos2D projects.
The Github project can be found here:
You can read more about the tool on the Cocos2D forum here:
Looks like a useful tool – and you can’t beat free.