esata (e for external) is the hot port these days, not the same as the internal sata. But you probably do not have that interface.
Personally I always have at least two hard drives on my sytem (including laptop) and setup shortcuts to quickly copy data to the alternate drive (client files drive & personal projects drive) for live backups.
Also I prefer to use a couple of 250GB external USB drives rather than put loads of data on to the latest huge drive. This way if I loose a drive i have not lost everything, and it is a second back anyway.
I've done a few raid setups, but with power loss I would have to recall and tweak multiple settings (bios, etc) to get back online, and this rattles the nerves. Got me to buy a UPS though!
There are some nice 2.5 inch 7200 rpm external drives on the market now, and if you travel with a laptop these are an attractive form factor.
The freeNAS raid 1 suggestion is wise also, or pickup a NAS from Fry's if you got the bucks and want a smaller footprint.
-Shea