Andrew suggested that we try Brightkite. It's a location based mobile social networking app. It does a good job of doing what others do, letting you "check-in" at different locations and then make notes about each location. Checking in lets your friends track you; and you can see where your friends are.
Unfortunately, all these sites still suffer from the problem of figuring out what "your location" means. Pretty much the only thing I can match on is an address (although once I do that, I can give it a shorthand name) and I just don't know the address (or fancy spelling) of places like University Towne Centre [sic].
The problem of figuring out what "place" means to a user is gonna get solved ... it just hasn't yet. (And GPS is not a solution in itself.)