World Google Maps Volcano Browser - Here is a Google Maps mashup of the earthquake feed from USGS. At time of posting this mashup draws from a database of 1550 volcanoes and lets you search these volcanoes by world region, location and specific type of volcano (eg: caldera, cinder cone, lava dome etc..) Of course when you have filtered your search, the volcano gets mapped to a nifty Google Map to provide some location relevance to the text listing.
Google Map of every Solar Eclipse - Here is an interesting Google Map mashup that lets you plot the viewing location of all solar eclipses from 1991 to 2030. Some of the eclipse viewing locations even have a great digital photo of what the viewing location looks like.
Other World Maps:
7 Highest Peaks on each of the 7 continents
Worldwide Trail Guide