Appointment Scheduler, an article which reviews Easy!Appointments and offers a tutorial for setting your own instance, has been published recently on Linux Magazine #269.
Easy!Appointments is a web application designed to let your customers book your services online. Do you run a clinic and want your patients to schedule an appointment with their Doctor over the web? Easy!Appointments has you covered! This web application lets customers book an appointment with their Doctor at any hour their need (assuming the hour has not been taken by another patient and that the Doctor is available). Every party involved may get email notifications for their appointments. It is quite neat for a free application.
Of course, it can be used for other scenarios. In fact, I first came in contact with Easy!Appointments when a customer, who runs a Beauty Saloon, asked me for a solution for letting customers book appointments in advance.
You may find the article in Linux Magazine #269.