Find below a list of tools to communicate and collaborate with the members of the wiki-section.
Conversation & deliberation tools
Adium A free and open source instant messaging client for OS X
Appear browser-based video-conferencing tool (no login required)
Jappix Jappix is an open social platform, that let's you easily get or keep in touch with everyone.
Mumble Mumble is a voice over IP (VoIP) application
Roundcube browser-based multilingual IMAP client
XMPP Clients List of XMPP-Clients (german)
Writing & editing tools
Open Knowledge Foundation Pad collaborative writing tool (without login)
Google-Docs collaborative writing tool (at least the owner needs login)
MixedInk collaborative writing tool (login required)
ShowDocument collaborative writing tool (login required)
Trello free project management tool (login required)