You can use just about any GPS and digital camera to geotag images. The most common workflow, with today's technology, is to sync the built-in clocks of the GPS unit and the camera and then simply turn on the GPS while you're shooting. Afterwards, you can use any one of the numerous software programs available to match the tracklog of the GPS (containing coordinates at periodic time intervals) to the exif data of the images.
Currently, I use a Garmin eTrex Vista Cx, Canon 30D and RoboGeo
BTW, in case you haven't seen it yet, if you have lat/long in your metadata, Adobe Lightroom has a direct link from the metadata browser to Google Maps. Click the button and a browser opens with Google Maps displaying the location of your image.