Axure - The most powerful way to plan, prototype and hand off to developers, all without code. Download a free trial and see why professionals choose Axure RP 9.
Timezone.io - Keep track where and when your team is.
Balsamiq - Balsamiq. Rapid, effective and fun wireframing software.
TimeZoneNinja - Scheduling meetings around the world just got easy
Moqups - The most stunning HTML5 app for creating resolution-independent SVG mockups, wireframes & interactive prototypes for your next project
Time Zone Pro - A beautiful world clock for friends, family, clients and more