Microsoft has a downloadable "Tag" reader app that scans images like this, which are scattered around the expo halls:
You can participate in the Web 2.0 Scavenger Hunt and win Zune HDs, Xbox Elites, and other fun prizes.
Everyone has smart phones nowadays, so this type of game would work at this conference. I am intrigued to see how many people will play, and how competitive it is.
One of the best parts of the scavenger hunt is the fact that you can win an instant prize just by using it. I downloaded the Android app for it, and had no trouble signing in and scanning a Tag.
Tag is easy to use, and Microsoft lets you create your own:
If you are at Web 2.0 Expo, give it a shot, and let me know what you think of it. Did you win anything?