hi michael
most external hard drives are the same however in my experience ive found "freecom" and "iomega" ...with the latter being in my opinion the best
iomega have been around for over 20 years and intially created the old tape driven storage devices which are still avalible today but at much larger capacitys .... however one of the best current iomega external hard drives is the "Iomega Prestiege 500GB Desktop Hard Drive "( http://www.ebuyer.com/product/206305 ) ... this is a excellent drive and has a stand for safe mounting... however its reliability is second to none.. and as soon as you use it you will notice how well its made...
however if you want something more compact then the "Iomega eGo 320GB Portable Hard Drive"( http://www.ebuyer.com/product/166862 ) is worth considering... its a robust little drive and comes in a sporting red colour scheme...and unlike the prestiege the eGo draws its power from the usb bus,,, this makes this more ideal for moving large files long distance....
freecom drives have also been around for quite some time.. and these tend to be cheaper than the iomega drives... however they dont sacrifice reliability with the savings...
in regards to drives i recommend the "Freecom ToughDrive 250GB Portable Hard Drive Turbo"( http://www.ebuyer.com/product/128918 ) .. this is a nice drive with encryption security and anti-shock features... so if this drops then it wont be damaged.....
it also supports a turbo feature .. which basically means it will transfer files faster when used with a usb 2.0 compliant port....
i hope this helps
good luck michael !