[wicker_man]

If you want a firewire drive, I'd reccomend Western Digital My Book range. I currently have two 1TB Studio drives (quad interface), and used to have 500GB and 750GB Pro drives which have all been fine.

If you are going to be using the drive for multiple computers or want to access the drive wirelessly at all times (for example with a laptop), then a Time Capsule would be better (and you would get constant Time Machine backups when connected to your wireless network. Alternately, you could get an Airport Extreme base station and connect a large hard drive (or more via a hub) to use as a wireless drive.

I'm not sure about content access to an Apple TV, but I believe as long as the content is in your iTunes library on a computer, then it can sync/stream to it. You can have content from an external drive in iTunes (change your iTunes music folder directory,) I have my music collection running from one of my WD My Book drives in iTunes.