Update: This guy is even more hardcore, he posted his photos and instructions for installation. And yes, caveat emptor: even brand new hard drives can fail, and poorly-designed casings can kill your drive too. James the guru points out that poorly-ventilated cheapo enclosures can kill your drive due to overheating, especially if you let it run all day. The man speaks from experience (he has a server rack in his house, for goodness' sake). I make no guarantees for this enclosure (I am trying it out myself). but so far it is running cool (the thing has an 8-inch cooler fan inside).
Found this neat 3.5-inch enclosure (Zoom Xtreme MS-35CB) that supports USB 2.0, Firewire 400 and Firewire 800 at Funan. I put a Maxtor 200Gb IDE HDD in it and backed up everything I had on the Powerbook. I haven't seen many enclosures that support the faster Firewire 800 port that is found on all new Powerbooks and Mac G5s, so this was a nice find, though it cost $30 more than the version with just USB 2.0 and Firewire 400.
It also comes in Graphite colour. There are several versions of this case, I believe, the cheapest being the USB 2.0 only. There is also a USB 2.0/Firewire 400 version, a USB 2.0/Firewire 400/Firewire 800 version (mine) and a SATA to USB 2.0/SATA to SATA version.
Casing is aluminium alloy, has an 8-inch turbo fan inside for cooling, on/off switch, and comes with a vertical stand, power supply and all the data cables you need.
I formatted mine for "Mac OS Extended" but you could format it as FAT32 for PC and Mac usage too.
Backup your stuff, or lose it. Hard disk prices have dropped so much. This 3.5-inch external drive cost me less than the 40Gb 2.5-inch portable external drive I bought a year ago. And that same portable drive now costs less than half what I paid.