This doesn't happen anymore, but when I was little, I would always have dreams about my teeth falling out.
These were more frequent back when I was in school, but I still occasionally have these dreams -- where I would miss the bus back home and get stuck at school.
Another school-related theme, I often have these dreams where I would be walking around in a school, wondering what class I need to get to, but I never really know, so I just walk into a random classroom.

(I think my brain knows how much I actually miss school)
Probably due to my love for astronomy, I often have dreams about the sky, mainly stars, the moon, and/or multiple moons. In a lot of these dreams, I would be looking into the sky, and new moons would just pop into existence.