I know this subject has been done to death but her is my solution:
I wanted an easy way to create multiple backups onto external data without the price tag of a rack/caddy system. I use a 24" imac so only have USB or firewire connections available.
I got
this from Geekstuff4u and picked up a couple of seagate drives very cheap.
Connected everything up (needed a UK adaptor plug) put the disks in and created two backups within 40 minutes - one for home and another for offsite.
As larger disks get cheaper I can by more (got 160 gig).
Seems a very cost effective backup method. I know you can just buy the connector wires on their own but this simple solution holds the drive well and has an on off switch and eject button.....