I agree that USB/FW drives are ideal.
But, not having the budget for one at the time, several years ago I bought a very inexpensive FW enclosure - like under $20 - for a 60GB IDE laptop HD I had leftover from an iBook repair for a friend.
The drive has proven invaluable, for that whole series of Macs that have FW ports but don't have USB 2.0 - most of the iMac G4s, the B&W G3s, the beige G3s, and so on. The drive has been a lifesaver (and time saver) so many times, when I needed to install an OS or transfer large file backups to or from these kinds of machines.
The only pity is that to use the drive with my '09 iMac (which has only FW 800 ports), I need to spend almost as much on a FW400-800 adapter as I did on the original FW drive enclosure itself.