Two of the most useful free (as in beer) software applications from Google are Google Earth, which runs on your computer, and Google Maps, which runs as a Web service. You can use both Google Earth and Google Maps to plot your own points, lines or shapes on an interactive map. You can also annotate these things with informative details. Unfortunately, the user interfaces provided by Google for doing this kind of DIY mapping are... well, clunky. They're slow, especially if you have a lot of items to add to a map.