Ahh, let's see what else I can think of... (I was really a terrible international student, I hardly went out exploring at all. /o\ ) The Guild Hall museum off Fossgate is pretty interesting! And King's Manor is not very far away from the Minster and neat to explore, plus the City Museum and gardens are right behind it and full of stuff (like the multangular Roman tower with Norman construction on top of it). I second walking around the walls, that's a lot of fun. And the Minster library in the old archbishop's palace is neat, though they don't have a lot of displays or anything. And the Shambles is nice to walk down (with a little shrine to a Catholic saint who was martyred in York, St. Margaret of Clitherow).