We use Setmore: http://www.setmore.com/ http://www.setmore.com/. Very happy with it and the developers are responsive to issues (even from free users like me).

We use Setmore: http://www.setmore.com/ http://www.setmore.com/. Very happy with it and the developers are responsive to issues (even from free users like me). I found many customers were booking appointments without figuring out the equivalent time in their timezone, missing their scheduled appointment because of the confusion. The devs added a new hover feature to make it clear what their local time is for available slots. We use the subdomain. Iframe integration is also available (not amazing on mobile).