Rupp, external as in for a PC or a set-top-box for using with TV? If it's a STB, I'd say holkd off for a while, they're as buggy as heck.
For PC-based, I like Squintz's recommendation. Just make sure your PC has good USB2.0. I recently had problems using an external USB2.0 HDD due to problems with the USB on my MoBo. A BIOS upgrade has sine fixed it, though.