Dudle - Dudle is an online scheduling application, which is free and open source.
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.
Pulse 24/7 - Booking & scheduling mobile app for service providers
Wrike - Wrike is a flexible, scalable, and easy-to-use collaborative work management software that helps high-performance teams organize and accomplish their work. Try it now.
MakePlans - Online appointment booking - MakePlans
Basecamp - A simple and elegant project management system.