I hacked together some cool javascript code that takes a world editable Google spreadsheet that contains names and longitudes and latitudes and puts them on a map. It is a really cool and simple way to allow people to add themselves to a map.
Here is the example: http://www.the-iliad.org/map.html
Here is the source: http://pastebin.com/LPVb5NPy
I am sure if you wanted to make it more complicated you could make it so people didn't even need to goto the Google spreadsheet and could just enter the information in a text box on the webpage and click a button. You can put the map in an iframe to do that.
This code probably has other cool applications.
