Followerwonk - Followerwonk by Moz is a Twitter analytics tool to help companies better understand their Twitter followers.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
burrrd. - A beautiful UI that provides you detailed twitter analytics.
Event Hunt - Startups and Tech Events Curated By Locals
Twitter Ads - Twitter offers targeted ad placement on their ad platform.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets