Meetingbird for Gmail - View your calendar and schedule meetings right from Gmail
Mixmax Calendar - The fastest way to schedule meetings with anyone, anywhere
Clockwise - Time & attendance tracking with QuickBooks integration
Kin Calendar - The simple and connected calendar
Schedulr - Schedulr makes it easy to meet with others w/out the headache of back-and-forth emailing.
Zynq - Schedule meetings from an email with 1 click!