Elm Street is the birthplace of Nobby Nobbs. It's also the place where the Fresh Start Club meets, at no 668, mainly to keep Reg Shoe happy. Cab drivers refuse to stop here, on the grounds that the horse will be up on bricks and the shoes gone, plus the wheels, in no seconds nothing.
Mrs. Evadne Cake's lodging house for residents with unique and particular needs (such as dog flaps and windows which can be opened by a paw) is also located here: famous inhabitants have included Angua von Überwald and Mavolio Bent (a seemingly normal human being who is arguably more frightening than any undead).
668: The Neighbour of the Beast was a working title for a possible sequel to Pratchett and Gaiman's Good Omens.