Well, the 7 in 7 board hasn't been quite as hopping as I might have hoped. So far it's pretty much been just two of us (Hi Pam!), and even I kind of bailed on her this week.... But for posterity's sake I thought I'd pull out a few of the theories that have been discussed.
First, if Dumbledore left something Harry will need in Book 7 (e.g. a memory or instrument or something) there are signs in Book 1 that point to it being left with Hagrid. During the very opening scene where baby Harry is delivered to the Dursley's, Dumbledore says, "I would trust Hagrid with my life." DD then goes on to trust Hagrid with several important things--Baby Harry, getting Harry from the Dursley's, the Sorcerer's Stone. As another clue about what Hagrid knows, when Hagrid tells Harry about Voldemort, Hagrid says "Some say he died. Codswallop, in my opinion. Dunno if he had enough human left in him to die." Later Harry remembers this when he sees the hooded figure in the Forbidden Forest. It's interesting that we later find out that that's exactly the case--Voldemort, in fact, didn't have enough human in him left to die.
Second, all the early occlumency/legilimency hints really make you wonder how much Snape knew about what the trio knew about the Sorcerer's Stone. (e.g. ...after Harry and Ron knock out the troll and are trying to explain it Snape gives Harry a "swift, piercing look." (pg 177) ..."Could Snape possibly know they'd found out about the Sorcerer's Stone? Harry didn't see how he could--yet he sometimes had the horrible feeling that Snape could read minds." (p. 221)) If he knew what was going on--and was truly Dumbledore's man--it puts a whole new credibility to the idea that Dumbledore allowed Harry to go after the Stone as a sort of training or test. Other evidence that supports that idea is the detention in the Forbidden Forest. All through the rest of the books detentions are things like writing lines and cleaning things--they never do anything dangerous. Why make them go into the Forrest unless Dumbledore wanted to make sure Harry knew what was there?