You might remember me freaking out a little about Firefox knowing my location quite accurately. Seems to be a fluke though. I gave my app to a colleague who tried it from his home, and his location wasn't anywhere close to reality. So it's not the most reliable way of finding where you are.
However, try running this on a device with GPS (say, an iPhone), and things improve quite a bit (which should be no surprise). I consistently got accuracy to within a few meters. This means that you can actually do some very interesting, fun and useful applications straight in the browser. E.g. leaving virtual tags in physical locations.
The Google maps API is pretty awesome, by the way. Adding maps to your website takes no more than five minutes of your time. And the flexibility offered is really quite amazing (select your zoom, map type; choose your controls, or define your own; add markers, popups, statistical data;...).
Also, Rails made it pretty easy to store and retrieve locations I've been to. That too was set up in no more than an hour (that's for someone who hadn't looked at Rails in quite some time).
So overall a fun and educational experience. And again some code to throw on the already quite sizable pile of unfinished projects.