I bought a Western Digital 'My Book' 160 GB External HD in August. One of the best investments I ever made. Did a little shopping around and ended up getting 50% off the regular price through price-matching. Reg. $180, got for $90. It's makes a bit of humming and vibrating noise when reading, but from what I have been told, even with the little bit of noise, it is the one of the quietest on the market. Externals have been around long enough, I don't really think there is a bad major manufacturer of them, out there.
http://www.wdc.com/en/products/products.asp?DriveID=217
Jam it back in, in the dark.