Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
BuildFire - BuildFire is the easiest way for small businesses to build a mobile app in a matter of minutes for iOS and Android.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Bizness Apps - Create your own app or become a reseller and build apps for others
Meetabit - All the local tech and startup meetups in one place - easy to organize & attend
Attendify - Develop relationships at the events that you attend by creating smaller events with just a few people.