Stormia - Beautiful animation of live weather in the US
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
US Health Weather Map - The U.S.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Dark Sky - Hyperlocal weather information, now on the web ⛈
Bigtent - BigTent is a web-based organization and communication portal for groups.