MeetMe - Location-based social networking app for meeting singles.
Empathy - Apps/Empathy - GNOME Wiki!
Badoo - Badoo combines elements of dating apps and social media platforms to create a unique way of meeting potential romantic interests.
Psi-IM - Psi-IM is a messaging program that is designed for the XMPP network.
Manjam - Manjam is the social network for gay men and their friends.
Gajim - Full featured and easy to use Jabber client