I just brought a Nokia 3120 which is triband, colour screen, small/light and will take a data cable so you can synch it with Outlook and download ring tones and applications etc. Cost me under £50 and I promptly went online and some kind soul provided an unlock code for FREE so it is now simfree. Amazon has been doing them for around the £50 mark but google is your friend. Ebay are good for things like data cables and dual sim card holders if you want to run it with a couple of different sims. The Nokia software is free from their website.
Used to be contract and go for the latest and greatest camera/mp3 etc but since going pre pay I am saving a bundle and have realised just how little I actually needed/used all of that extra whizz bang stuff.