Tools for managing and scheduling meetings with students?
Several of my colleagues use YouCanBookMe (https://gb.youcanbook.me/), which integrates with GoogleCalendar. You can specifiy "office hours" or the like, and then students can book a meeting with you.

I myself, however, discuss individual appointments per mail and then immediately add them to my digital calendar, which to me works better, as I do not have fixed office hours.

When I want to have a whole day of meetings (e.g., everyone from a class is supposed to have an individual meeting with me on one specific day to get feedback), I create an etherpad at http://www.titanpad.com , give timeslots and ask all students to put their names on it.

For group meetings with colleagues, I use http://doodle.com (or http://datumprikker.nl , which offers a similar service in Dutch) to schedule group meetings. I guess pretty much everyone at our department does so.