Followerwonk - Followerwonk by Moz is a Twitter analytics tool to help companies better understand their Twitter followers.
Calendify - Calendify is an event community where you can share, publish, and subscribe to event calendars. It helps you to stay informed about what you are interested in and what is yet to come.
burrrd. - A beautiful UI that provides you detailed twitter analytics.
Morse - Create, shout out, and discover nearby events in real time
Twitter Ads - Twitter offers targeted ad placement on their ad platform.
Upcoming.org - A simple way to share and discover interesting events