There are a lot of ways to do this, like encoding a jpeg with an entire song or using some arcane hexadecimal gobbledygook to ask a girl out on a date (reliable sources say it works every time). Or if you're a total show-off you can learn to read a binary clock. I don't know how to do any of that, but check out what I can do:
Who cares, right? It's a two-dimensional bar code. Well, people who like to move fast and keep their contacts organized, that's who. Not only does that contain all of my (fake) contact info, it's arranged for easy importing. Scan this with ixMAT from the Android Market, and you can instantly add me to your contacts - all of the information will go where it belongs; name, email, website, etc.
Tane Piper, the coder writing Brightroid - an Android client based on the location-aware social network, Brightkite - turned me on to ixMAT Scanner. (I'll be reviewing his program later - it's in the early stages now.) He sent out his contact info in the form of a QR image, and I had to know how he did it. There are plenty of sites that can make one of these for you, but the link he offered has the most consistent, standardized formatting of the five-or-so I tested.
You can render in three different sizes, making them perfect for the sidebar of a blog, the signature at the bottom of an email, or as the wallpaper on the homescreen of your G1. Now that's a practical application. And you'll WIN at any gathering of geeks.