Meetingbird for Gmail - View your calendar and schedule meetings right from Gmail
Calendly - Say goodbye to phone and email tag for finding the perfect meeting time with Calendly. It's 100% free, super easy to use and you'll love our customer service.
Kin Calendar - The simple and connected calendar
SavvyCal - A scheduling tool both the sender and the recipient will love.
Calendly for Chrome - Schedule meetings without leaving your inbox
Cal.com - Cal.com (formerly Calendso) is the open source Calendly alternative.