[Update 12/15/2012 : Effective January 2013, appointment slots will no longer be an option. Try YouCanBook.Me instead.]
Google Calendar now lets you let others schedule appointments in your calendar. With YouCanBook.Me, any open time can be scheduled. With Google Calendar’s new feature, you decide which times are open to scheduling.
In Google Calendar, click on an open time slot like you normally do to add a new event. Click on “Appointment slots”.
Call it what you’d like, say, “Office Hours”, then I selected “Offer as slots of 30 minutes.” Change the time to another amount if you’d like, such as 15 minutes. That’s it. Edit the details if you’d like. Add a location, say. This is where you get the URL to the appointment page that you will give to your students. Expand the amount of time you want to make open for appointments. After adding three time slots, this is what my calendar looks like.
Here’s the URL to my appointment calendar where you can only see the times when I’ve blocked off.
Note that those who wish to make an appointment this way will need to have a Google Calendar account.
Once the appointment is made, it’s added to both my calendar and the appointment-maker’s calendar. If they delete it from their calendar, it will also be deleted from my calendar, and the time slot will once again be available to future visitors.