Catching a cab during the 2012 London Games might be impossible, if not for TaxiBaxck. TaxiBack is a new UK-based startup that connects those in need of a cab with cabbies who need a fare. In order to use the service, you must know your starting point and destination ahead of time, so you can't exactly use it for spontaneous trips, or for nights out.
If you are someone who likes to plan ahead, then TaxiBack will be perfect for you. Once you submit your itinerary, the site will send you three bids from registered cabbies. Since the cabbies are competing against each other, you're sure to get a discounted rate. The cabbies win by booking guaranteed fares a day in advance, and the consumer wins by not having to hail a cab and haggle a fare.