I just learned about a fantastic new service called Setster which is targeted at service providers, consultants, and freelancers. (= People like me!) Setster allows you to list your availability in an online overlay widget on your site and allows customers to book appointments, pay for services etc. (I love to hear hat Setster integrates with Freshbooks, to allow service providers the ability to invoice from within the Setster Application. Yes, I am a Freshbooks Fan!)
You can see what a sample/pretend Setster widget overlay on swissmiss would look like by clicking here. It is a free service with upgrade options, clean UI and very designer friendly, non intrusive button that follows users around the site until they decide they want to book 60 minutes of your time for a gazillion dollars.
They just launched the widget so they do not have too many sample sites but check out this Designer’s Site with the Setster widget installed.