I looooove Acuity!!
It's probably my most indispensable tech tool and I honestly wish that EVERYONE I ever made an appointment with would use this. It's that good.
Try it yourself for free at http://bbrshow.com/acuity
Listen to the story of how Acuity Scheduling came to be in my interview with the founder Gavin Zuchlinski on episode 98 http://bbrshow.com/podcast/1394