Your post brings something to mind. Who were all of the people that Voldemort killed that come out of the wand? There are Cedric, the Potters, the old caretaker and VM's father, grandfather and grandmother. I don't have my books with me, but is that all?
Now, ignore Cedric as Voldie didn't kill him. That leaves six murders. We (Dumbledore) assume there are six horcrux. If a horcrux has to be made soon after the murder, the ones at the Riddle house would probably be the ring, the locket, and the diary. The two at the Potter's are unknown unless one is Harry. The old caretaker would have provided the murder for the snake, or something else in the old house.
If my facts are wrong let me know. The assumptions are mine. I assume these were all of Voldie's murders since they came out of the wand, but if he used another wand elsewhere we don't see it. Also, I don't remember if he killed the caretaker or if Wormtail did it on Voldie's order. That would mean we need to find another murder by Voldie. It could also lead to Harry being a horcrux in a strange twist of logic.
I am reading the whole series again--it has finally been returned to me after a long loan. In Sorcerer's Stone, when DD and McGonagall are outside the Dursley's waiting for Hagrid with the baby HP, DD mentions that 11 long years of terror are finally over. He also makes mention of the scores of murders that VM has committed. I have forgotten all of this over the past few years.