Walkaround - Walkaround is a variant of Wave, based on the Apache Wave code base, that runs on App Engine.
Waver - Description: Google Wave is a great way to communicate and collaborate. Waver lets you:
Rizzoma - Email and IM are linear contextless communication tools.
Slack - A messaging app for teams who see through the Earth!
Tlk2me - Tlk2me is simple real-time messaging platform which is designed exclusively for groups.
Microsoft Teams - Microsoft Teams provides the enterprise-level security, compliance and management features you expect from Office 365, including broad support for compliance standards, and eDiscovery and legal hold for channels, chats, and files.