Portable Firefox CX is a portable profile switcher written for Mac OS X in ObjC/Cocoa. It's designed to give a simple interface to execute a local copy of Firefox.app with a specific profile, choosen from a list.
You should just download the DMG and add Firefox 1.5 in the application folder. For other Firefox version make sure that the profile included is compatible. At least one profile MUST exist. The application handles multiple profiles.