I recently found a website that increases the "Whoa, cool!" factor up several orders of magnitude for GPS's. If you have a GPS unit you need to check this place out:
www.GPSVisualizer.com This website allows you to upload your tracks and waypoint files and convert them into a number of different views. You can convert your files (any GPS manufacturer) to files readable by any other GPS unit.
You can overlay your tracks on a topo map of the region.
You can overlay your track on an aerial photograph of the region.
You can overlay your track on a satellite photo.
You can even plot your changes in your altitude!
Uh, this last one is much more interesting when you actually DO change altitude...
You can also convert your track into
Google Earth .kml or .kmz files. Then you can see your track overlayed on Google Earth and do a bird's eye flight of your path.
This is really neat if you are a map freak!
-Mark