Calendly is a great freemium tool for letting other people schedule events on your calendar

Finally! An elegant solution for sharing your free/busy calendar information with anyone in the world and allowing them to book events.

Calendly works with Google Calendar, Outlook, Exchange and iCloud. The premium version allows you to let people schedule different meeting lengths. But I find the free version works reasonably well. I use 60 minutes as my standard event duration, and then have a custom question on the form that allows people to indicate they want a shorter meeting.

Calendly—meeting scheduling tool