HDD Encllosure

I'm going to buy a new laptop, and I'm planning on buying a 640GB Western digital caviar 16MB cache and using it externally (obviously), with an HDD enclosure. However, I know nothing about this devices and would like some advice and suggestions on which one to get. I've heard this is extremely delicate hardware, and needs to be top notch no matter what. Ok well, I'm open for suggestions .

You're referring to the disk drive, I presume? The enclosures are pretty much commodity items and I don't think there's a very strong reason to go with one or the other. I've standardized on the aluminum VanTec NexStar enclosures and have been quite happy with them.

Regarding the robustness of disk drives: these are actually more rugged than a lot of people given them credit for, at least when they're not running. I wouldn't want to drop one, but when they're powered down they can be bumped and jostled without any problems. For ease of mind you'd probably want to visit the manufacturer's website and check the specs for the drive to ensure that it has a mechanism to unload the heads from the platters when the power is turned off. For example, this page describing the 640GB WD Caviar Blue shows that it uses "NoTouch ramp load technology".