I just got round to buying one today after umming and ahhing over it for about a year 🙂
Went for a Maxtor Basics 2.5″ drive, 250gb. Plenty big enough as my PC is 160Gb and my lappy is 120Gb.
It is £58 in Currys/PC World, I reserved it online at £44 then went and picked it up instore a couple of hours later which avoids the £5 delivery charge.
Up til now I’ve used a second internal hard drive to back up my stuff, I plug it in, transfer files and then take it out and put away for safe keeping. I was expecting the new external drive to be slower being USB2.0, but copying 48Gb of files took longer on the internal SATA drive. (Both drives were on the same channel, primary and slave, so that might slow it down a bit)