More Londoners than ever are using contactless payments to get around the capital, and now, a new initiative called "Penny for London" is asking commuters to add charitable donations to their daily routine, too. The idea is that every time you use a contactless card to pay for travel, you also put aside a nominal amount -- between 1p and 10p -- for charity. Then, at the end of the each month, Penny for London charges the accumulated total to the same card, and forwards the money on to the Mayor's Fund for London, Cash for Kids, The Prince's Trust and other charitable organisations. To get involved, all you need to do is register the card you use to travel on the initiative's website, where you can also keep track of your donations, set up caps and change other preferences. While Barclaycard is responsible for developing the "micro-donation" system, any Visa or Mastercard can be used. The hope is other retailers that accept contactless payments will also sign up to participate in the initiative, but for now, at least you can feel like you're embarking on cramped, uncomfortable Tube journeys for a good cause.