Go to NewEgg.com and buy a Firewire enclosure for about $40.
This is a good one.
Then look for a deal on a hard drive. NewEgg has 'em of course, but you might even check places like OfficeMax and Staples for deals. A lot of times you can get them for REALLY cheap after rebates. Check DealMac of course... and if you really want it now and don't want to wait for an awesome deal to surface, NewEgg has pretty good prices. A 160 GB hard drive with 8 MB buffer is $113 there. Total cost - $153. Sure, it won't look quite as awesome as the LaCie D2, but you have to decide whether the nice-looking enclosure is worth the $30 extra.
I've noticed that LaCie and other companies have gotten more competitive with the prices on their external hard drives. I remember a while back I got an 80 GB hard drive for about $70 and an enclosure for $40, while every external 80 GB hard drive was either $180 or $200. Things have certainly changed, and you might actually want to get the LaCie for the extra style and slightly reduced hassle.