I know a lot about the work of religious men in the Medieval/Renaissance/Baroque/Etc periods, but there were a lot of religious women making music at that same time too! So what (if any) unique contributions did they make to music? Any techniques, compositions, styles, and such that came from nuns?
You might look at Hildegard von Bingen, whose importance is becoming more clear as research on her deepens. Hers is the first extant morality play, which you could say is her biggest contribution to culture at large. She also has some important early liturgical dramas. Aside from that, her music is truly stunning, I think. Margot Fassler has been working on Hildegard a lot lately, specifically on the Ordo virtutum. Here's her article from a couple years ago on the subject: