I think I heard somewhere around here that hallows are holy or sacred ground, so it could be 'holy' in Voldemort's eyes in that it's important to him. (I'm paraphrasing from another post here, apologys).
I think that perhaps Godric's Hollow (that's where the Potter's lived, wasn't it? It's been a while since I've read all the books) will be important. I think it's the word "Hallows" that makes me think this, for some reason.
Apparently we find out something important about Lily, but I swear that was reputed back when book five was about to be released or something, and all we found out was that she hated James before she started liking him.
Also, one of the characters apparently becomes a teacher at Hogwarts after everything is over and done with. As I've said around here, my first guess was Hermione, but perhaps it could be someone else, even someone like Neville (herbology), or maybe even an older character. *Shrugs* Anyway, enough with the guessing, we'll find out anon (well, perhaps not anon, more like a few months!)
One last thing...I think that Ron and Hermione will finally get together. I believe this is a very real possibility (especially after all the hints of such throughout the books) Either this will happen and one of them will be killed, so that there is a tender, tear-jerking moment between them as one lies in the others arms, OR they'll keep avoiding the inevitable until one is on their deathbed, and then they'll finally admitt it.
Anyway, these are just my ideas, of course! All we can do is wait until the final book comes out (Of which I am glad, finally it's coming to an end!)