While NFC has yet to be widely adopted in smartphones, that didn't stop Google from sneaking it in to the Google+ app. This mean that, when using an NFC-enabled device (read: the Nexus S/4G), you'll be able to read tags and share the contents via Google+. The functionality is quite limited right now, but this could bring big things in the future: automatically check in at a restaurant and share it with your Circles, scan tags to join a Huddle, easily find location-based relevant Sparks... the list goes on and on.
Unfortunately, the only way you can utilize this functionality is if you have a Nexus S and are part of the Google+ field trial. The rest of us, however, can live vicariously through this video to experience the joys and wonders of NFC with G+: