Because I tried to build an autonav before, happen to have a Google Maps API key, and understand much of the code I was able to throw this together in about 15 min
http://maps.juhlin.com/test.html
You can drag, zoom, and flip map/satellite the map via the portion you can see on the bottom. When you zoom it zooms the "center" of the underlying map (which is not the center of the circle). It takes a bit of trial and error to get what you want but with this you only have to crop out the bottom portion of the map.
Thanks to LBraden for the template.
Edit; Made it so you can drag the whole map now. Ie not supported (use the bottom of the map) Firefox 3.6+, Safari 4 and Google Chrome should be good.