A piano has 88 keys; Ohio has 88 counties. Cartographer Andy Woodruff noticed this fact while driving through Ohio to complete his Counties Visited Map, and decided, despite knowing nothing about music, to make a map based on this coincidence.
Trulia Hindsight merges real estate data showing the year properties were built with animated maps (US Only). Search for your town by name; here's mine.
The Imperial History of the Middle East is a flash based map of the Middle East, with a sliding timeline showing the various forces that have established dominance in the region over the last 5,000 years. Just one of many interesting interactive demonstrations over at Maps Of War.
"CabSpotting traces San Francisco's taxi cabs as they travel throughout the Bay Area. The patterns traced by each cab create a living and always-changing map of city life. This map hints at economic, social, and cultural trends that are otherwise invisible."
FlashEarth is a Flash app that adds continuous zoom and rotation abilities to Google Maps/MSN VirtualEarth. Created by Paul Neave.