BeWelcome - Open your door to the world!
Dudle - Dudle is an online scheduling application, which is free and open source.
Trustroots - Travellers community for sharing, hosting and getting people together.
FullCalendar - FullCalendar is an open-source JavaScript event calendar.
Couchsurfing - CouchSurfing is your ticket to explore the world -- from the road or from your own home.
Framadate - Make your polls