Edoodz lets you tag or draw on Google Maps.
If you press 'Paint' you can then draw on top of a Google Map satellite image of anywhere in the world. Edoodz has some simple drawing tools. You can change the brush size and its brush. You can also rub out your mistakes.
Once you save your drawing it is added to the map. When you get bored of drawing you can browse other users' pictures by clicking on the 'Click to Tour' button.