[img src="" caption="" credit="" alt=""]
GeoCommons is the latest mapping service which enables users to create geographic data and use it to create custom, intelligent maps. Think of it as the mix between Swivel and Google Maps.
It works like this: you can take a geographic data set and choose which parts you want to use. For example, say you want to use the calorie consumption in various US states dataset to create a map. You can take data from 2002 and 2003, and focus it so that only states above a certain number of calorie consumption are visible. Then, you export that to Google Earth's KML or CSV format, and you get a nice, custom map. Or you can go to your GeoCommons workplace, search for data from there, and directly add it to your map (you can use several layers of data), which you can save and share with other users.
The maps themselves are based on Google maps, but the data is presented in the form of shapes and heat maps, which is visually very effective, but unfortunately, in practice it's sometimes a bit slow.
GeoCommons is quite an advanced service, and although it can be used for fun, businesses, professionals, and geoenthusiasts will make more use of it than casual users. It takes a while to get used to all that it can offer, but once you do, the results can be very rewarding.