qBittorrent - Lightweight and open source torrent client that runs on all major platforms.
Zenly - Zenly is a GPS tracker to locate your friends in realtime.
Deluge - Deluge is a full-featured BitTorrent client for Linux, Unix and Windows.
sup - The first creep-free way to see nearby friends
BitTorrent - BitTorrent is a peer-to-peer program developed by Bram Cohen and BitTorrent, Inc.
Babble - A more personalized social network