Instructions on how to patch your Apple TV to use external USB storage has been released at AppleTVHacks.net
Installing the patch is a somewhat involved effort which also requires version 1.0 of the Apple TV software (current version is 1.1).
As a result, they are asking for more help to bring this patch to the masses.
We are aware that the USB Patch released on Friday night was pretty restrictive on the requirements: Intel-Mac, OS X files, Apple TV Software 1.0, etc. Now that the source code is out in the wild, we would like the community to investigate these issues and submit improvements over the existing code.