Really Cool Map Mashup

I have to admit--I have always been VERY social. So when I saw that a PA group started for NECC attendees I was very excited. Now I would be able to tell which of my friends in my networks were going to be there....but Atlanta is a big city, how would I know where everyone was staying?
I started by creating a google map--only to discover that I was the only one who could add placemarks. So I started my quest for map mashups that would allow multiple users to add bookmarks.....I have always liked frappr, but found that when I was on my district network I was unable to access it. Then I found platial. The basic concept is this: you create a map of a certain locations, add bookmarks and people can comment on the bookmarks you added or add their own. I created a map for PA NECC attendees so they could add the placemarks of where they were staying--neat because it could be embedded into the wikispace for the PA group as well.
Platial has some pretty cool maps....like good eats in NY and some cool features, like you can limit who can add to your map.....Then I started to think about OTHER more educational applications. What about creating a map of the battles of Gettysburg. Teacher can bookmark the sites, students can comment on what happened there. OR a map of natural disasters--kids can add the location and others can comment. If you are visiting my blog today--take some time to click on my platial map and let me know where you are visiting from!!!!