This past Friday, during a discussion of Google maps (while using it to find something on my phone), Feilim Mac Gabhann alerted me to a site called Wikimapia.
It’s Google Satellite, but you can draw a box and then describe what’s in the box. Which boxes are shown depends on your level of zoom, so it’s both scale-appropriate and manageable.
This is the coolest thing I’ve seen in a while, except maybe the iPhone. You really should go check it out.
ADDENDUM: You can also load the information in Google Earth as discussed in this blog post. Even cooler!