Well, you can set appointments in the default calendar, or basically any calendar app, like Jorte.
It would all depend on what exactly would you want from an appointment program. The default calendar can set an alarm, time, date, duration, location, participants and notes regarding any event like an appointment you would have for that particular day. Then there are several software that are supposed to enhance the calendar features. (practically any phone/tablet nowadays could do this appointment feature on the default calendar)
Here's what will come up if you type appointment on Android market: