WrongZoom is an open-source SIMBL plugin for Mac OS X 10.5 (Leopard) and 10.6 (Snow Leopard) to change all Cocoa apps to make the green button maximize windows instead of zooming them to fit content like Mac OS X does by default.
If you're not a developer, you probably want to download the plugin. Once you've downloaded the plugin, make sure you have SIMBL installed, then copy WrongZoom.bundle to ~/Library/Application Support/SIMBL/Plugins/.
Please feel free to fork this project and make improvements!