MapsGeek.com has just launched, and describes itself as:

MapsGeek.com is a free website designed to allow anyone to easily build or access thematic maps and share them with the world.

Equipped with a powerful blend of features, MapsGeek will guide you in the map's making and let you publish this map on your website, blog to illustrate your articles. Moreover, by making this map public, other MapsGeek users will be able to update the data: your map is alive and never out of date !!!

The biggest draw appear to be the choropleth maps. Shaded area maps are a doddle for many offline applications (eg. Microsoft MapPoint) but are generally lacking from online applications such as Google Maps and Bing Maps, due to the need for large polygon definitions. MapsGeek.com is definitely not the first online choropleth map application, but it does appear to have deeper (ie. smaller and more detailed) polygon definitions. It is not clear how fine they go. For example, can it go as far as zipcodes, postcodes, and census tracts  like MapPoint can?