Machine tags and Google Sky
Scripting the Google Earth plugin to display an area of sky around the Horsehead nebula. The parameters for the plugin script (coordinates, field size, orientation) are grabbed from flickr machine tags on a picture of the nebula. The machine tags, in turn, were generated by the amazing astrometry.net bot.
You can see this working live at eatyourgreens.org.uk/testapps/yql/