The methods described on this page require advanced javascript knowledge, and are not officially supported. They are included in our official wiki because certain shipping methods and functionality are not natively supported, and though we are working on radically improving our shipping functionality, in the meantime these methods may be great workarounds. Use with caution, test, and post in our forum if you run into problems.
The information for this technique can now be found here: http://wiki.foxycart.com/snippets/shipping/multiple_flat_rates