Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Waver - Description: Google Wave is a great way to communicate and collaborate. Waver lets you:
TidyHQ - Organization management tool to support membership, subscriptions, event planning, and outreach.
Rizzoma - Email and IM are linear contextless communication tools.
Mighty Networks - Mighty Networks enables entrepreneurs, organizations, and companies to create and grow a community-powered brand.
BSI Knowledge Manager - Central document management & knowledge base