Don't want to take my word for it? Take a look at what Amanda Hess has to say about Youcanbook.me in College & Research Libraries News:
Hess, A. (2014). Scheduling research consultations with YouCanBook.Me : Low effort, high yield. College & Research Libraries News, 75(9) 510-513.
Charlotte Price and Gina Levitan presented on Youcanbook.me for the SUNYLA 2015 conference. You can find their handout here:
Youcanbook.me (YCBM) is a cloud-based scheduling service that allows others to easily schedule time with you. YCBM works seamlessly with Google Calendar and iCal. At the library, we use YCBM to let students schedule appointments with us for class or reference questions but YCBM is flexible and can be used to let students/patrons/people book time with a specific person, one of a group of people, or an item or space. Some features of YCBM require a subscription, but all the basics are free.
There's plenty of options to make YCBM fit your needs and style but the basic set-up is extremely easy and can be done in about five minutes. Then, others can choose times to meet with you that work for both of you. The event is automatically added to your calendar and you're notified by e-mail. Maintenance is as simple as keeping your calendar up to date.