About the last remaining relic being the sword--you're right! I read someone today venturing that when Tom Riddle controlled Ginny in CoS, and said he "poured his soul" into her, he made her a horcrux. I have always thought that the Weasly's must be some distant relative of Gryffindor becuase of the red hair (everyone comments on it), their very strong bravery and loyalty, and in the PoA movie (which Rowling consulted on), Ron takes the candy and makes a lion roar (remember, Neville makes the elephant noise, and Harry sounds like a train). So, if this was true, Ginny would be a remnany of the Gryffindor bloodline, wouldn't she? And how awful for Harry to have to kill her, or at least consider the option!
Speaking of the Weasley's and the red hair, and connection to being an heir of Gryffindor.
I remember in one of the books that Harry sees a picture of a young Dumbledore (where he is looking at pictures of the Black family on the wall? I forget) and it describes Dumbledore as having red hair.
It would explain why Dumbldore's hair is described as "silvery". I've always known that red-haired people, when they turn grey, turn the most wonderful color of silver. I'm waiting for mine to go completely grey so I can stop coloring it, and then BOOM! I'll be a silver-haired fox.
Anyway, just thought I'd mention the part about when Dumbledore was younger, his hair was red.