1. Flickr Related Tag Browser: type in any tag word, search and any related photo on flickr will appear in the middle of the page, surrounded by related tag words...click on one of those and the photos tagged with the new term will appear with the new related tag words.
2. CIA World Fact Book Visualization: Allows to visualize relationships between countries that includes borders, surrounding countries, languages, and bodies of water. This is a great application for a history / geography class to demonstrate the connections and proximity or distance of countries to one another.