Compulsively draggable click-toy
Google Maps has added satellite imagery to its site; you can now switch between line-art maps and satellite photographs, all zoomable. Some regions don't have satellite imagery at the highest resolution.
Interestingly enough, while the maps are still North America-only, you can drag the satellite view to anywhere in the world; most parts of the world don't let you zoom in to any level that shows signs of habitation though.