T-Mobile - Nokia 6600

If you're so inclined, one using a Nokia Series 60 phone (such as the N-Gage, 6600, or 7610) and Cellspotting software can get information on their location via cellphone. Cellspotting will give you the current location and name, and will direct you to locations or even other friends who are using the service by identifying particular location IDs that a cellular tower recognizes. Since the service is relatively new, there's not too much information in their database, but that should change as they roll out Cellspotting for more cellphones.

[Via textually.org]

Burton / R.E.D. Audio HiFi Helmet