PayPal recently released an iPhone app for sending and receiving money. You may request and send money to other PayPal users, as well as view your payment history and withdraw money from your account. There is also a cool feature for making it super easy to split a check with any number of people!
There is even a novelty feature where two people who are both using the app can bump their phones together to automatically pair them for easy money transfer. It uses the GPS to get the location of nearby iPhones and the bump time to find the correct one.
This is a great way for handling money among friends, and it is super easy too! It really makes it possible to be without cash and transfer money electronically without using credit cards — most friends probably don’t have their own card swiping machine.