If you need information on land use changes over time, or on current land uses and character, you may want to check out decades-worth of globe-spanning satellite images that USGS made freely available to the public on Dec. 30, 2008. The Landsat images (via instruments on board Landsat 1-5) were taken from 1972 to the present. On Oct. 1, 2008, USGS took a similar step with Landsat 7 images taken from 1999 to the present. The various instruments capture different kinds of information about the earth.
- USGS, Landsat images: Group on Earth Observations;  Landsat Missions;  Global Visualization Viewer;  or EarthExplorer. 
For questions, contact Jon Campbell,  703-648-4180.