Dumbledor explains in book six what he knows about the horcruxes and i'm inclined to believe him. As i have just recently re-read book 6 i an comfortable in saying there are 6 horcruxes and 7 parts of his soul. The book and ring were destroyed. We assume whoever R.A.B is destryed the horcrux in the locket, but that wasn't confirmed, in the letter is R said he was going to try do destroy it. I think it is destroyed, but then who knows. So we have the ring, book, locket, also the cup of hufflepuff, nagini and something of ravenclaws or gryffindors. Dumbledore believed it was somthing of ravenclaws and i'm inclined to believe him. If we take all the information Dumbledor gave Harry the only horcrux we don't know is the thing of Ravenclaws, so 6 parts of Voldemort's soul are horcruxes and the 7th is inside voldemort himself. Anyone have any idea's what ravenclaws horcrux could be?