This might be a possible solution for some of you using Google Calendar to schedule resources and spaces in your schools. Give it a try and let us know what you think!
"Appointment slots in Google Calendar: Posted by Irene Chung, Software Engineer Google Calendar has become indispensable for organizing my own time and sharing my schedule with..."
"Every Google Calendar has its own personal appointments sign up page; you can embed it on your website or give the URL directly to friends and clients. You can find the URL for your appointment page at the top of the set-up page, which you can access via the Edit details link."