This video demo of the free PayPal app is great fun, using a couple of guys sort of in the same vein as the "I'm a Mac" commercials. A version just released lets you Bump to exchange money. You hold your iPhones, bump fists to exchange contact information, and then send money with a tap. Plus, it has tools built in that do things like help you split a check, request money, and calculate a tip. You can also quickly send money to anyone in your contacts list. Read more about it in the New York Times.