John Gruber (daringfireball.net): "Should be a built-in iPhone feature."
Handshake is the free app for your iPhone™ or iPod Touch™ that makes it easy to pass your contact entry to another user nearby. You can also pass a different contact or even a photo!
No more typing. No more typos. It just works!
For a brief demonstration of Handshake, please see our YouTube video:
Also available, for US$2.99, is Handshake Premium, which provides the same experience advertisement-free and karma-enhanced.
Additional resources: