The best bet is to make your own with an external case and an internal hard drive. That way you control the drive's quality and can make sure it has cooling, an essential component for a capable, durable external drive.
I suggest the AMS Venus case (
http://www.newegg.com/Product/Product.asp?Item=N82E16817145652) since it has onboard cooling. It looks nice, is very quiet, and really keeps your drive a low temperature. I assume there are other cases from other manufacturers, but nothing seems to come close to this one.
After that, just get any cheap HD you can find. I suggest Seagate - they usually offer the longest warranties and are considered some of the highest quality. You could easily put something together for around 100 and have 120+ gigs or more.
If you want an all in one unit, find one with cooling. I can't stress that enough. When I made my exernal HD about 6 months ago, I found that cooling was essential and that putting one together yourself gives you much more flexability. I'd really suggest that route unless you find a killer deal on an all-in-one unit.
Good luck.
Edit: Per below post, here's the FW + USB2 version (slightly more expensive) of the Venus case: (In Silver)
http://www.newegg.com/Product/Product.asp?Item=N82E16817145655
(In Black)
http://www.newegg.com/Product/Product.asp?Item=N82E16817145657
Wheee fun, they have silver ones now.
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