Google Calendar
Google Calendar lets you organize your schedule and share events with co-workers and friends. With Google's free online calendar, it's easy to keep track of your daily schedule.
Apptoto
For appointment-based businesses, Apptoto offers automated SMS text, email or voice reminders and online scheduling
Artichoke
Artichoke is a business platform for freelancers: everything in one place, on any device, wherever you work. A web page for booking online, automated reminders, one-touch payments, searchable progress notes, and simple solutions to take control of the numbers for today’s freelancers.
MashApp
MashApp allows you to automatically track your marketing campaigns and sales results in a calendar.
TIMIFY
TIMIFY is an online scheduling and resource management tool for all kind of small businesses and large enterprises.