The US Postal Service are doing the first useful implementation of augmented reality that I've seen. You can find out which size bracket your parcel falls into. You can see a video of how it works here:
http://www.youtube.com/watch?v=WpS3LeCiCtc
I've seen fun uses of it, the best being the music video for Ride My Star:
http://www.julianperretta.com/ride_my_star/
More information here:
http://www.marketingvox.com/augmented-reality-technology-brings-useful-service-to-usps-044353/
