Google Maps introduced a new feature recently that can determine your location when using their mobile version from a cell phone. If your phone has GPS available it can use that to get a pretty precise location, otherwise it can somehow determine which cell tower you are on to get you an approximate location. That is pretty powerful.
I wonder, though, how Google is able to determine which tower you are using. That has some pretty big potential privacy issues if anybody you call or send a text message to, or any website you visit from your phone can somehow determine what tower you are on.