I learned from Fred Wilson that Flickr has just added geotagging, the ability to add latitude and longitude to each of your photos. It’s a good design - you just drag and drop photos onto a map of the world. I quickly tagged 30 or so photos from our travels over the last nine months, plus a few from previous trips. The results are here.
I would like to have a camera (or cameraphone) with integrated GPS so that all my photos could be tagged with time, date, and place. It’s one of the most obvious location-based services, but I am still waiting for it.