Any way to hook up an external hard drive to an appletv?

Not without warranty voiding hacks which we can't talk about here.

Now if you want to buy an external drive and want it available to your AppleTV you can attach external drive to the computer you sync with.

Then configure iTunes to use it as your library thus the AppleTV will use it.

I have my computer using a 1TB external drive as my iTunes library drive thus the AppleTV reads/syncs to/from it.

HELP L:OOKING FOR SOME SORT OF INSTRUCTIONS HOW TO SET UP ITUNES TO AN EXTERNAL HARD DRIVE SO I CAN COPY (TO EXTERN HD) THEN DELETE (FRM MY COMPTRS HD) RUNNING OUTT OF ROOM ALL MY MOVIES AND MUSIC AND ALSO HAVE THE CAPABILITY TO USE MY APPLE TV WITH THE EXTERNAL DRIVE