Thanks to dauphin1974 for this pointer to Wikimapia. It's essentially Google Earth with a wiki attached to it -- you can define regions on the "world", and wiki entries for those regions. He recommends (and I concur) drilling down to Cambridge, and looking around; I see that the Harvard crowd has already defined a bunch of the buildings and stuff there. Unfortunately, the search function doesn't seem to work correctly yet. But it's still fun to play with.