Brightkite

I've been prostelytizing for Brightkite since I got in on their public beta. A location based social network service is only as good as the other people on it, from where I sit. When I joined the Brightkite beta I didn't know anyone on the service other than the person that I'd gotten my invite from, and even that person was a twitterfriend. In response to that I tried to get all of my friends onto it so that I could actually arrange meetings and let people know where I am and have them show up.

One ITP student did exactly that. I was having dinner at Half King and I checked in via brightkite. A few minutes later one of our ITP classmates showed up to say hello because he lived around the corner and it was convenient. I don't think this leverages even 10% of the power of locative services, but this is one of the only experiences I've had of them working.