Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Hypefury - No idea what to share on Twitter?
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
What to Tweet - Never again run out of Tweet ideas.
Bigtent - BigTent is a web-based organization and communication portal for groups.
Toolset.com - The complete and reliable plugin for managing content types in WordPress.