Recommendations for an Appointment Scheduler?

Hi, all!

We're going to start promoting our demos at events by asking attendees to schedule appointments in advance.

Can anyone recommend a good appointment scheduler?  There are so many to choose from - I'm about to take a trial of BookFresh, but I wanted to see if anyone has used something else that they can recommend.

A lot of them that I've looked into have a bunch of added funtionality for the price, but most of that isn't needed since we have Marketo (I won't lie, though - the text reminders some of them offer are nice).  We also don't need to accept payments.

Thanks for any help!

~Jenn