WeatherTunes - Weather based radio and music discovery
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
EventsApp - A simple concise app for creating and sharing events.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Sparq Events - 3D Social Networking
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.