I recently bought a Maxtor (or is it Seagate?) OneTouch III external hard drive. It's a pretty sweet drive, maybe a bit big and noisy, but perfect for my needs - backing up my systems. One really nice thing is that it's totally Mac-centric: it ships preformatted with HFS+, it supports Firewire 400 and 800 (nice with the new iMac), and it includes Retrospect Express backup software, which originated on the Mac, as I recall.
It include a button on the front that you can program to do various things, the most obvious being to initiate a backup. But it didn't work; I'd push the button and nothing would happen. After poking around, I found this update for Intel Macs. After installing it (and rebooting), it works like a charm.