NeighborhoodBase includes maps and data from a number of city agencies, plus census data. All data is available for aggregation at a range of geographic levels (ie, wards, census tracts, etc). A great source for data and maps about life in Philadelphia.

Here are examples of different ways of projecting the Earth's surface and a brief discussion of the pros and cons of each of the methods.

The US Census provides thematic maps at various levels of geography and for many data points.

Allows users to store, tag, and share locations -- based on google maps, but does interesting things. Users add photos of places, and lots of other tagged info about the places.

The Valley of the Shadow is a digital archive of primary sources that document the lives of people in Augusta County, Virginia, and Franklin County, Pennsylvania, during the era of the American Civil War. Here you may explore thousands of original documents that allow you to see what life was like during the Civil War for the men and women of Augusta and Franklin.

This section shows the routes of battles of union and confederate soldiers in the area.

The Great Britain Historical Geographical Information System is a unique digital collection of information about Britain's localities as they have changed over time. Information comes from census reports, historical gazetteers, travellers' tales and historic maps, assembled into a whole that is much more than the sum of its parts.

Historical Maps plus GIS from the David Rumsey Collection.

While many businesses were in the path of these storms, some were affected and others were not. Knowing where affected businesses are concentrated can guide efforts by Federal, State, and local agencies, service organizations, and entrepreneurs to respond to the storms and rebuild the economies of these areas.

State of Louisiana EPA map-making site.

In this interactive web site, you are able to select a city or metropolitan area and view the location of high-poverty census tracts and observe the growth of high-poverty areas over time. In addition, you may view the changing demographics of the population. All of the maps here are based on U.S. Census data from 1970 through 2000. The data are summarized at the neighborhood level, using Census Tracts as proxies for neighborhoods.