Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
ilo - Premium Twitter analytics
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Tweetastic - Better Twitter analytics, scheduling and more
Bigtent - BigTent is a web-based organization and communication portal for groups.
Twitter Interactions - See all your interactions 💬 with other Twitter🐦 users