Icybox 390 (which is out of stock on OcUK ATM) or there's the Icy Dock MB-559US. Both have eSATA + USB2.
A good choice of drive to go with that is the WD Green 1TB - quiet, low power and reasonable performance. High performance drives are overkill *unless* you want to run programs from the external drive (only a sensible option if using eSATA). For simple storage USB2 is OK-ish, but eSATA is again far better with at least 3x the speed. The speed difference is really much more marked than that (3x equals the approximate difference for maximum transfer rate), because in normal use USB will never operate at it's quoted max speed.
I have 8 external drives, 3 in Icyboxes (USB2), 1 a WD MyBook (FireWire400), and the remainder kept off-line and connected using a Sharkoon (USB2) when required. I find USB2 painfully slow most of the time, especially dealing with small-ish files (photos and music files). If you find it necessary to move 500GB from one drive to another as I did recently you can look forward to a >12hrs wait. I'm envious of those that can get eSATA to work reliably, it gives me problems but I think it's the WD MyBook hardware which is the cause (it is the only drive I have eSATA capable but it's an old version).
Firewire, despite it's max burst speed rate being lower than USB (400Mb/sec c.f., 480Mb/sec) is actually 20% faster for sustained data streaming.
