This is a beautiful site.
The Atlas of the Biosphere, a service of the Center for Sustainability and the Global Environment at the University of Wisconsin-Madison, is a wonderful resource for global and regional maps of environmental data. The maps cover four broad categories: human impacts, land use, ecosystems, and water resources. Global and continental maps are available for each subject, all approximately 1600x1200 in size (making them perfect for desktop backgrounds). The map description pages include Geographic Information Systems (GIS) data for ESRI ArcView, the widely-used GIS software, allowing the creation of new mapsets.
The maps give country-based information for most human activity subjects (such as infant mortality, proportion of population under the age of 15, and per capita oil use) and more precise gridcell-based information for most environmental subjects (such as net primary productivity, built-up land, and lakes and wetlands).
Beyond the maps, the Atlas of the Biosphere also has a set of system schematics, in Flash format, showing processes such as the carbon cycle and the Earth's "radiation budget." The SAGE group takes advantage of the SWF format for animation, which is nice, but not for interactivity. Perhaps in the next iteration.
SAGE describes the Atlas as an "ongoing project," and they encourage suggestions for additions.
