Don't have a GPS device that works with your camera? You can manually enter locations at your PC with GeoSetter. After you do, the application shows your locations as pins in a Google Maps pane built into the program. GeoSetter updates the executable image file format (EXIF) details so that locations will appear in other apps. Geotag data is stored in your pictures for you to browse in GeoSetter or other tools, including Flickr, Picasa, and SmugMug.
Note: This program is donationware. It is free to try, but the author accepts and encourages donations towards further development.