Gyroscope - Gyroscope is a personalized dashboard for tracking your life.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Exist - Track everything in one place, understand your life.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Reporter App - Reporter lets you track the things you care about with a few randomly timed surveys each day.
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.