Xmind - Xmind is a brainstorming and mind mapping application.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Event Hunt - Startups and Tech Events Curated By Locals
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets