Sheep - Membership and events for SMEs and nonprofits
TidyHQ - Organization management tool to support membership, subscriptions, event planning, and outreach.
Galette - Galette is a membership management web application towards non profit organizations.
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
NationBuilder - The world's first platform for leaders, handcrafted from scratch to help you grow your community and lead them to action.
Membee - Membee is web-based membership management software.