external hard drive

Depends on your size requirements, but I just bought this. Note the 8mb cache size (important for speed) and support for fw800 and usb2 (which are both "backwards compatible to regular firewire and usb, respectively). I plan on using with a G5, so FW800 is useful to me, and for your purposes you never know if you'll be using 800 with a computer in the future. A little more than $1 per gig is pretty good for an external fw800 supporting device, and LaCie is one of the best (i've heard) with regard to reliability, etc.

Another possibility would be to buy an external casing for a normal IDE/ATA drive and then the drive separately so that if you decided to in the future, you could stick the hard drive into a desktop. You might find some good deals on that, too. In any case, I started at pricegrabber.com. Maybe not the best search site, but I was happy with my results!

Addendum: regarding brands, I've traditionally looked at LaCi, Seagate, and to a lesser extent, Western Digital (cheap). Apparently the Maxtor ones are getting better but I'm still hesetant. There are other high end brands, of course, but they can get very pricey, and if this i just a "backup" drive, you might want to just go for something huge and cheap. If you don't care about speed at all, some of the Lacie's with 2mb buffer cache are cheaper, but for a discussion on that stuff you could check out my thread from a couple days ago here.

Good luck!

without trying to sell a particular product, I suggest trying LaCie. http://www.lacie.com/ They have numerous storage solutions. We have used many from a simple 2gb HD to CD & DVD burners and other optical drives. I myself purchased a Maxtor http://www.maxtor.com/ 60gb internal HD for my b&W G3 that was easy plug-n-play.

I have to recommend Other World Computing

If it's just for backup, the cheapest route would be a build-your-own FW400 case with an inexpensive hard drive; speed really isn't that important, since it's backup, so FW800 isn't a big deal, and an 8MB cache isn't so important, either (though buying 8MB cache drives generally gets you a 3 year warranty, which might be worth it.

This is generally what I've done in the past, although buying a kit can be cheaper than buying a drive and case seperately, if you find a good deal and don't have an unused IDE hard drive laying around (which I did).

Personal recommendations: OWC (http://macsales.com -- good support, inexpensive, Mac-centric) makes nice, cheap FW drives (try their Neptune series). Do NOT get a Maxtor drive; those, in my personal experience and backed up by anecdotal evidence, are the least reliable of the major manufacturer's drives, so I wouldn't really want to rely on one for backups. Seagate are generally the most reliable (and cheap), though I've had good luck with Samsung drives over the past four years.