free download of images, books, data: http://www.usgs.gov/ 

free download of Modis images: http://rapidfire.sci.gsfc.nasa.gov/cgi-bin/imagery/realtime.cgi?date=2011299

free download of Landsat images: http://glcfapp.glcf.umd.edu/

free download of worldwide map (Street map) http://www.openstreetmap.org/