Along with many other Harry fans, I have horcruxes on the brain.
Before I start discussing them in any detail, I think it would be useful to lay out what we already know. Assuming Dumbledore is correct, there are 7 horcruxes and we know what at least 4 of them are....
- Tom Riddle's Diary
- Marvolo Gaunt's Ring
- Merope Gaunt's Locket
- Helga Hufflepuff's Cup
In addition, Horcrux 5 is probably something that belonged to Rowena Ravenclaw. Horcrux 6 could be an object that belonged to Godric Gryffindor, but Dumbledore believes that's unlikely, therefore so do I. I think it's more likely that Dumbledore's guess is correct and the Horcrux 6 is Voldemort's snake Nagini. Horcrux 7 is anyone's guess.