After buying a mobile broadband contract for my wife, I was sent details of the UK Property Register. It basically allows anyone to record their portable property that is at risk of left (usually things like mobiles, laptops, bicycles). Once registered it means that the Police can more easily identify your item if it is stolen and you can more easily record it lost or stolen.
After having two bikes stolen over the last few years, this seems like a very useful free service that everyone should know about. Visit http://www.immobilise.com to sign-up today and let the Police know what is yours.