A pilot project in San Fransisco uses these mobile codes for restaurant reviews. Restaurants display their unique codes which link to a page on a service called Citysearch where users can enter their on review of the restaurant. Another useful service is activation of audio guides on specific locations around the city, activated by scanning the code which will take you to a page on a site run by Discovery Channel.
Essentially, the potential for these codes is to bring information from the digital world into the physical world by creating a link to a specific website. The software needed is easy to use and can be downloaded to any phone running Java. Nokia supplies some of their phones with the software preinstalled, others are likely to follow.
Another project worth taking a look at is Semapedia, which intends to tag everything in the world around you with a link to a Wikipedia article via QR codes. It is community driven and relies on it's members creating and printing the codes to be placed where the link is going to be.
Everyone has been talking about the mobile internet revolution being well overdue, but I think this is going to be one of the major factors to get people to make the leap to go online while on the move. Of course, better handsets with bigger screens are a key factor as well, but rather than focusing on mobile adaptations of regular websites, the use of mobile codes are taking advantage of the handsets' most unique feature - mobility.