Meetingbird for Gmail - View your calendar and schedule meetings right from Gmail
Cal.com - Cal.com (formerly Calendso) is the open source Calendly alternative.
Mixmax Calendar - The fastest way to schedule meetings with anyone, anywhere
Cron - Cron Calendar.
Zynq - Schedule meetings from an email with 1 click!
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.