Pushover - Real-time notifications on your Android, iPhone, iPad, and Desktop
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Wildfire - With Wildfire, companies & agencies can easily build & launch social media marketing campaigns within minutes. Campaign formats include quizzes, contests, coupons, virtual gifts and more.
Event Hunt - Startups and Tech Events Curated By Locals
WonderPush - WonderPush makes it easy to target, personalize and automate push notifications on mobile applications and Websites
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets