Connecting the drives externally won't have any detremental effect on the laptop. Any drive case will have its own power supply so there it no extra strain on the battery/power brick for the laptop.
I have a couple of these:
http://www.scan.co.uk/Products/Produ...oductID=465786
They work well. Very useful as they can take a SATA or IDE drive and connect with either USB2 or eSATA (one SATA drives can connect with eSATA, it doesn't convert IDE to SATA). I also have a ExpressCard with two eSATA ports. I ended up geting mine from Play.com (
http://www.play.com/PC/PCs/-/667/874...e=3471558f2570) as i needed it quickly. You can get them on eBay cheaper, but delivery times from Hong Kong are a pain.
I also have a two port SATA PCMCIA cardfor my old laptop. Can't remember where i got that one from.