Have you heard of Sign Up Genius? This is an excellent FREE website for parent/teacher conference sign ups or any other sign ups you might need for your class, school, church groups, etc.. Once parents sign up for a time slot, Sign Up Genius will email them a day (or however many days ahead of time you select) in advance reminding them of when and where their conference will be held. It will even sync their appointment with their iCal or Google Calendar! Check out this tutorial I created that shows you how to make your very first sign up:
Sign Up Genius from Julie on Vimeo.