Harry's tale must have reached its end, but the fandom lives on. :) Here are Harry Potter theories/ideas I came up with or found interesting at the peak of the HP madness (most especially before, during, and after the release of Harry Potter and the Half-Blood Prince). I put a check on the ideas that turned out to be true in the last book.

• Dumbeldore is not dead. I remember seeing a website called Dumbledoreisnotdead.com. They offered pretty interesting theories.
  • Dumbeldore himself has a horcrux--his phoenix Fawkes. He defeated Grindelwald, and it wasn't mentioned how he defeated him. Since there aren't any information about Grindelwald being in Azkaban, it is assumed that Dumbeldore killed him--making Dumbeldore capable of splitting his own soul and making a horcrux for himself. Learned from book 7: Grindelwald wasn't dead.
  • How Snape cast Avada Kedavra--the effect on Dumbeldore was weird. And slow.
  • His wand was nowhere when he died. Nowhere during his funeral either. According to Hagrid & Slughorn's song regarding a common wizard tradition, a famous wizard's wand is publicly broken in honor of the said departed wizard. Learned from book 7: Draco was master of it. But he didn't know. Voldemort stole it from Dumbledore's coffin.
• ✔ Snape is on the Order's side. I mean, what was the extent of the Unbreakable Vow? And Snape wasn't truthful when Bellatrix and Narcissa talked to him. He seemed to have lied about still having Voldemort's trust. He must have used Legilimens to find out what he was pretending to know (when he was looking out the window).
• Bellatrix will live. I like her. And loved Helena Bonham Carter playing her. Molly killed her. Curse to the heart. Voldemort was mad.
• ✔ RAB is Regulus Black. Meh. Saw it from a website somewhere. Wikipedia, I think. I remember being surprised that there's a wikipage for him.
• ✔ Mundungus has the locket. I especially like how the locket went from RAB, to Grimmauld Place, to Kreacher, to Mundungus.
• Draco and Hermione will end up together. Sweet couple they would've made!
• Luna and Harry will end up together. Hey, it can happen! And I'd be happy if they hooked up. ;] Who didn't notice the chemistry they had in the OTP movie?
• Oliver Wood will be mentioned again. Seriously. Whatever happened to him? He's hot!

BTW, my favorite books in the series: Sorcerer's Stone, Goblet of Fire, and Half-Blood Prince.