If you're a Topographic Map fanatic like me, then you'll appreciate this. Google Maps, which fairly recently added a terrain view option to go with the standard map and satellite views, has just added contour lines. There's a brief discussion, with samples, written by the intern who did the work in this blog post.
To see it for yourself, launch Google Maps, go to your favorite area, and click the Terrain button:
Then zoom in so the scale bar is within 1 mile or less, and the contour lines will magically appear:
This can come in very handy for planning your next geocaching outing. Just another tool for the tool box.