Good Gear Guide
In Pictures: 10 cool and useful Google Maps mashup...
New Maps Help You Find Old Maps
The Old Maps Online project is a Google Maps mashup that helps you find historical maps from libraries across the world. To find an old map, position the main map over the area you're interested in and slide the controller at the top to browse through dates. The results--displayed as thumbnail images of the relevant old maps--appear at the right, and you can click a thumbnail to go to the corresponding image on the hosting institution's website.
In Pictures: 10 cool and useful Google Maps mashups