My pair of Formac 160GB rotating back-up drives were full so I needed something bigger. I got a pair of GoFlex 1TB drives which came with USB interfaces. I got a single Firewire pluggable interface to share between them. One drive is sitting in the Firewire dock getting backups stored on it while the other is rotated out offsite.
A £5 Firewire 400<->800 cable let me plug it into my iMac.
