Clocks - A minimal world clock app for your Mac's menubar
World Clock iOS 8 Widget - Check the time, anytime. Just pull down Notification Center.
Clocker - Keep track of people in different time zones
144blocks - Colorful way to track your time! Inspired by Wait But Why
Every Time Zone - Online tool for keeping up with times around the world.
Spacetime - Work hour and time zone management for distributed teams.