It's not even close to being massmarket yet, but geotagging is one of the technologies I'm personally most interested in, especially if it gets automated enough that the people using it don't even need to know what geotagging is to make use of it.
ShoZu's announcement this week that it's including geotagging in its Share-It mobile application is a step on the road. Users with GPS-enabled phones will be able to automatically attach location information to photos and videos when they're captured, and then have this uploaded along with the content to whatever sharing service they're using.
Currently supported are Flickr and YouTube, along with Buzznet, Pikeo, Dada.net, moblogUK and Textamerica. For Flickr, images will automatically be added to the user's Flickr map.
Now all I have to do is get myself a GPS phone. Anyone got any Nokia N95s going spare? ;o)