Frapper is a new-to-me site that allows anyone to create a theme for a Google map and overlay pins to represent just about anything you can put on a map. I could see this being used for some pretty neat class projects, like creating a map of historic sites or keeping track of current events.
In a more immediate example, Alexander Russo at This Week in Education is using the concept to sponsor an educational blogmap. If your blog fits the category (Go ahead, wedge it in there. I did. :-), drop by and stick your pin in the map.