Here is a visual guide to creating multiple Firefox profiles and set them up to run like separate applications on Snow Leopard.
Creating a new Firefox profile
Open terminal and execute the following command:
/Applications/Firefox.app/Contents/MacOS/firefox-bin --ProfileManager
This should bring up the Firefox Profile Manager -

Go ahead and create a brand new profile.
Using Automator to run the new Firefox profile as an application
Now, on to creating a proper Mac application to run Firefox with your chosen profile.
- Open Automator
- Choose File -> New -> Application

- Choose Utilities group under Library
- Drag Run Shell Script to the workflow pane on the right
- Paste the following script:
/Applications/Firefox.app/Contents/MacOS/firefox-bin -P MyProfile -no-remote &> /dev/null &

Replace MyProfile with the name of the profile you created earlier
- Choose File – Save As, and save it wherever you want to keep it. Leave the File Format as Application in the Save dialog.
Making it pretty – Changing the Application icon
- Right click on the saved file and choose Get Info ( or use Cmd + I ) to bring up the Info window.
Make sure that it is not locked (bottom right corner) -
- Open Finder and go to /Applications/Firefox.app/Contents/Resources directory.

- Open firefox.icns file in Preview (just double click it).
- Click on the image shown in the main Preview pane, copy it using Ctrl – C, click on the icon in the top of Info window and paste it using Ctrl – V.

And that is it, your new Firefox Application is ready to go. You can open this even when you have the default Firefox running. And, of course, you can create as many such application as you like.
If you’d like to give different icons to different profiles, just download an icon set and use that with the above steps. One of my favourites is Carbon Firefox, or try a Google search for icons.