Geo-Tag Mapper is a simple free tool for plotting geo-tagged images on a globe.
Launch the program, point it at a starting folder, and it will scan that folder tree looking for geo-tagged JPEGs. A globe (using KDE's Marble project) is then displayed where the position of each image is highlighted, while the status bar tells you the total number of images scanned, and the number of geotags found.
If you can't see all your photos immediately, try clicking and dragging to rotate the globe, or spin the mouse wheel to zoom in and out. (You can also navigate from the keyboard by using the cursor keys, and zooming with the plus and minus keys on the numeric keypad.)
As you spin the globe you'll see red "P" symbols highlighting each photo position. Click one of these to display a preview of that image.
Version 1.1 fixes a big with coordinate signs.