Last Updated Jun 9, 2008 12:21 PM EDT
A free Genbook account entitles you to unlimited online scheduling, unlimited staff/service offerings, a Book Now button you can embed on your site (or a site like Craigslist), and even optional solicitation of customer reviews. If you want text-message notification of new appointments, an online customer database, and support for credit-card transactions, you'll need to upgrade to a Standard account ($39.95 monthly).
I haven't tried Genbook myself, but it looks like a solid way to provide appointment scheduling to your customers. It would be nice if you could embed the actual calendar into your site as with Acuity, but otherwise I'd say Genbook has the edge in features and finesse.