Calendly is simple, effective, and worth it!

We use it to book appointments both externally, and internally, as we are a remote team. A key feature is the time-zone adjuster. I'm able to easily set up meetings with my colleagues on other continents without worrying too much about whether or not we will all have the time correctly on our calendars. It's also helpful that it automatically sends out Zoom meeting information so that people know how to join my meeting.