AVRMacPack and Xcode
The AVRmacpack for AVR development on the Apple Mac contains command line tools. These are all well and good if you want to do things the traditional way with text editors, terminal windows and make files. No real problem. However, if you want the benefits of a modern IDE with things like function lists and refactoring, you might want to try Xcode. It is, after all, supplied with your Mac.