The room booking system we had in place at our school was needlessly complicated, and prone to changes.
A lot of teachers at my school were frustrated with the booking system we had. I figured it would be a good exercise, trying to make our own internal booking system. It was a fun experience setting it up (except for dealing with time), and I got a MVP deployed relatively quickly.

The landing page for the booking site
Video showcasing the app (the capture software did not record the date/time pickers)