Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Membee - Membee is web-based membership management software.
Ticket Tailor - Ticket Tailor is an easy-to-use event ticketing platform that allows event organizers of all shapes and sizes to sell tickets online.
Galette - Galette is a membership management web application towards non profit organizations.
Cvent - Cvent's event management software provides event planners with a complete solution to increase event attendance and decrease event costs.