Rooting around at school I found this marvellous piece of nostalgia. Loads of carols I'd love to do at church but maybe the vicar isn't brave enough. Have a look at these lists, I guarantee some of them will come flooding back into your head. Let us know your favourites in the comments, and I'll paste up the sheet music and videos.
Altogether now: "It was on a starry night, when the hills were bright..."