In general, geotagged landmarks maps like this one are great ways to introduce geotagging. Teachers might ask students to bring in one image that students (with their parents) take and bring into class. Set up some basic requirements for the photos (e.g. no recognizable people, structure should be clearly identifiable, images should be in a .JPG format) - then create a gallery on a photo sharing website (e.g. Flickr, Google PicasaWeb, Panoramio) and let the kids contribute their images. It's often helpful if students bring in the address of the landmark, to help speed the geotagging.
