Here’s my own little contribution: fullscreen-map. A webpage which does nothing but display a map, remembering the current position and zoom. Why is this useful? Because it makes a very handy Active Desktop item.
For a while now I’ve had a satellite view of the neighbourhood as my desktop wallpaper. Set this page as a desktop item (Control Panel → Display →Desktop → Customize Desktop → Web → New) and I can have a live map on my desktop.
I’m not sure how useful this is—it’s mildly annoying that the Maps controls fall exactly where the desktop icons normally would—but it’s fun; I keep reaching off the sides of windows to jiggle the map underneath.
Feel free to link or steal, although if you copy it to your own server you’ll need to sign up for your own Maps API key.
[Updated July 16th: added the Scale control.]
[Updated July 24th: persist the Hybrid map type setting.]