StockMapper [stockmapper.com] (note: works only during U.S. markets are open...) is an online stock heat map, representing the performance of all common stocks listed on the NYSE Euronext. The heat map renders the individual percent changes in market value for more than 1,800 U.S. and non-U.S. stocks. Users can filter the stock quotes by logical groupings such as geographic region, industry and major indices. The map can also be sorted by ticker symbol, price change, volume or market capitalization. Upon selecting an individual stock group a "bridge bar chart" appears of the price change and trading volume of all stocks in the group.
Interestingly, StockMapper was originally designed as a non-interactive map of the market to be shown on a number of exterior data displays outside of the NYSE's Wall Street building.