Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Four Hour Book Club - 300+ Books recommended on the Tim Ferriss Show 📚
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
XdoX - Start challenges, log your progress and also get a unique profile page!
Bigtent - BigTent is a web-based organization and communication portal for groups.
Bookcelerator - A curated directory of books that will make you smarter