Now this is a cool mashup and its built right into Virtual Earth! In Wikipedia, you may have noticed that some articles have coordinates in the upper-right hand side of the page that locate that place on a map. (See this example). Clicking on the coordinates from the Wikipedia entry will take you to you a map. But if you want to go the other way - from a map to Wikipedia - then you've got to check out what the Virtual Earth team has done. They've been indexing all these links in their Spatial Search and Explore indexes so you can surf the maps with Wikipedia displaying in the sidebar. If you want to try it out for yourself, turn on Live Map's Explore feature and then select the Wikipedia Tag, or just click this link to see it in action now.