1. Go to: qrstuff.com
2. Select "Contact Details"
3. Select vCard & fill in your info
4. Click DOWNLOAD
This QR code will add your contact info to people's address books if they scan it. You can create QR codes that can do lots of things. For example, you can create codes that will direct people to follow you on Twitter, like a page on Facebook, or compose an email to you.
[kirkmc adds: Another hint from robleach. I haven't tested this.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20121123042859822