At last someone has developed a patch to expand the Apple TV's storage through its USB 2.0 port, using the internal hard drive to boot and one fat external 2TB drive to stockpile as many TV series, photos and porn movies as you want. Yes, Cupertino, resistance to hackers is futile, I'm afraid. The process is not difficult, as you will see after the jump.
For this recipe you will need one ssh-enabled Apple TV, one sightly battered Intel Mac or Intel-based Linux/Unix system, one installed version of Mac OS X 10.4 Intel, one clean, "original, unmodified copy of the 'mach_kernel.prelink' file from the Apple TV," one external USB drive, generous amounts of sightly peppered raw courage and a liberal quantity of chilled sherry.
For cooking, first format the external USB drive as Journaled HFS+ in Mac OS X and leave it aside. You won't need it until the end.
Run the script and back up your Apple TV using the included instructions. Now drink some sherry. After five minutes the Apple TV will reboot. Turn it on again without connecting the USB drive until the flying-TV-screens introduction sequence finishes. When you connect the USB the contents from the internal drive will be copied to the external one. That's why the chefs for this recipe, Patrick Walton of University of Chicago and Tom Anthony from Apple TV Hacks, recommend you to "erase the content of your internal hard drive first so that there is no need to copy the content." Finish the sherry or pour yourself another glass.
The Apple TV will restart automatically after the content is copied and from that point on the USB disk will be used as content storage. Unfortunately this will leave the internal drive empty save for the operating system - but, quite frankly, who cares when you are going to end up with a 2TB Apple TV, specially after all that chilled sherry?
If you think the process to enable what should have been a feature since the beginning is not for the faint-hearted, hopefully someone will release a graphic patcher soon. Otherwise, go for it carefully and enjoy. [Apple TV Hacks]