WD MyBook Pro - 500 GB. Comes with USB2/FW800/400, is virtually silent, fantastic performace and has some cool features. Fairly sure you can daisy-chain them via FW800 too.
It looks great and is pretty cheap.
Definately recommended. 😉
This is what you really want (less than $300):
One Expresscard 34 eSata Card
One Two bay hot swappable hard drive enclosure . Hard drives included.
Speed.... Lots and lots of speed. You may not actually need it, though.
I love my Lacie 250 gig ... runs around $180, but has been consistently functional (and pretty sexy too, I think). I connect to my PB via FW 800 and data moves fast enough.
can you find one with a sata splitter? in other words, one that uses just one sata port?
I've got La Cie 250 GB and 500 GB external hard drives for use with my iMac and MBP, and they have always worked just great for me. When I travel I use the La Cie "Rugged," which is 80 GB (I believe they also have a 160 GB version), as it is small and easy to stick into luggage or laptop bag.