OK, so I'm putting this into the misc section but I think it should be made HOT and put onto the front page :P This is why.
I discovered this service offered in the US called PricePinx, basically they have a system set up where you create an account and add a button to your browser window. When you see something you want to monitor the price of, you highlight the price and press that button, and hey presto it monitors the price and e-mails you when it drops.
This is a great system for watching the price of absolutely anything sold online and with some real work can be a huge bargain finder when reductions happen.
Anyway I've been testing the service out and it works fantastic, the only thing is that the site will use a $ instead of £ but if you ignore that then roberts your mothers brother.http://www.pricepinx.com/