Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
GroupSpaces - Free Group Website, Membership Database, Listserv Mailing List, Online Group Management Software : GroupSpaces
Bylde - Bylde is a SaaS platform you can use to Start, Manage and Grow your groups and communities.
The Groups Place - The Groups Place is a new alternative to Meetup.
SmartMoneyMatch - Create a 100% free account to connect to the global asset management industry. Get access to the best money managers or list your investments, RFPs, jobs, events, business services, and more.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets