Code generation tool with long Macintosh history, by Spec Bowers, one of the original FileMakerPro authors (before selling it to Claris who then became Filemaker.com).
Visually edit screens, menus and specify commands and data definitions.
Generates range of C/C++ output including (of course) PowerPlant and via the add-on AppMakerForWindows will generate MFC code.
There are demos on CodeWarrior CD's and downloadable from the home page http://members.aol.com/bowersdev/.
I (AndyDent) have worked on a number of code generators and used others. AppMaker is impressively flexible, being like Smalltalk IDE's in that the dictionary of generatable objects and their property dialogs are all soft-defined within AppMaker's metamodel so you can extend them. The full source code of the code generation templates is included - I enhanced the PowerPlant one to include our OOFILE database engine and then went on to develop the MFC generator with only the publicly available documentation and the original template sources.
On bigger projects, I've found the ability to write your own code generators very useful - AppMaker ships with several utility scripts I wrote, eg: cross-referencing all commands so you can tell if someone linked the wrong command to a button, cross-referencing all pictures.
Version 2 was reviewed in MacTech? http://www.mactech.com/articles/mactech/Vol.13/13.04/AppMaker2.0Review/ and an article on customizing PowerPlant generation followed - http://www.mactech.com/articles/mactech/Vol.12/12.12/CustomizingAppMaker2/.