Glympse - Glympse is the easy way to safely share your location in realtime. No sign-up needed.
Party with a Local - Party with a Local is a free app that connects travelers with locals that want to party.
Zenly - Zenly is a GPS tracker to locate your friends in realtime.
Palaround - Meet people you should be friends with.
OwnTracks - Cross-platform location sharing
Babble - A more personalized social network