I know Chabad has the custom of staying up all 7th night of Passover. What is the source and does anyone else do this?
Otzar Minhagei Chabad says that the Sefer "Minhag Israel Torah" says that there was an old Chassidic custom to stay up on the seventh night of Pesach and say over miracle stories. However, some aren't happy with this custom (it doesn't say the reason in Otzar Minhagei Chabad and I don't have a copy of Minhag Yisrael Torah).
Presumably, the reason to stay up all night is that since the Jews received such great revelations at the sea, we want to "relive it" again