Italics are impressions from my first read, when I did not yet know what was going to happen.
1) The lost diadem. Not Muriel's after all, I bet, but the one Harry used to mark the location of the half-blood Prince's potions book in the Room of Requirement.
2) Neville is the King of Awesomeland. I swear, there is not one character in this entire series who had grown as much as this boy. From timid underachiever to the head of the Hogwarts resistance movement. I love him so much.
3) Neville calls Aberforth "Ab". *more Neville love* So Aberforth's not living under a secret assumed identity; the Death Eaters are just stupid. Look! Look! Dumbledore's brother, right there in Hogsmeade! They suck.
4) Neville has summoned some other people who will be Apparating directly into the Hog's Head. He tells "Ab" how it's going to be and does not ask permission. This really is a whole new Neville! And such a gentleman, giving Hermione a hand up into the passage! Was Neville already planning to come see Aberforth and tell him this, and it's a coincidence that the Trio arrived at the same time? Or has Neville just now decided to make the party bigger?
5) The secret passage. I think it's a feature of the Room of Requirement, and only exists when it's needed.
6) The Gringotts break-in. It really has raised morale. Neville is all impressed by what the trio has been up to, but I'm more impressed by him.
7) The Carrows make Umbridge look like one of her kittens. They've turned DADA into just Dark Arts and Muggle Studies into mandatory propaganda sessions. And they are in charge of punishments. The DEs is just full of sadists, isn't it? I suppose they would be especially attracted to a regime under which they have power and privilege to lord over other people.
8) Crabbe and Goyle are awesome at Dark Arts stuff. Neville mentions them especially as excelling, probably because it's such a big change from their usual academic achievement. But if they are capable of this stuff they can't be as stupid as we've thought, can they?
9) Neville: "The thing is, it helps when people stand up to them, it gives everyone hope. I used to notice that when you did it, Harry." Heroic!Neville + Harry/Neville moment = best thing ever. This is totally my postwar 'ship. I also love that Neville pushes the envelope as far as he can, knowing that his pure blood protects him. They don't want to rough up their breeding stock too much. It's weird hearing him speak so casually of torture and the Cruciatus curse, considering what happened to his own parents. It speaks volumes about the kind of year he's had.
10) Dumbledore's Army, Still Recruiting. The Neville love just doesn't stop. I cannot express how much I love this boy. You know, if polyjuice flavour reflects the person's moral character, I wanna know what Nevillejuice tastes like! OK, that sounded wrong.
11) Gran's on the run! Go, Gussie! That goes a long way toward making up for the way she used to treat Neville. I haven't entirely forgiven her yet, mind you.
12) Neville's been living in the Room of Requirement. He's as much a marked man now as Harry. The Death Eaters have not managed to get into it. The way Seamus describes Neville's understanding of the Room of Requirement, it sounds almost like the room loves him and wants to keep him safe. But how will Harry get the diadem if Neville and the DA are in a different version of the Room? Can they just ask the Room to change into the Hiding Place around them? It would seem like they could, since it can do *anything* people need it to do.
13) Everyone's overjoyed to see Harry. But they also call out to Ron and Hermione. Awww...they have fans, too!
14) Seamus: "Neville's the man!" I could not have said it better myself. I'm adding that statement to my LJ interests. So there.
15) The Room can't do food. Well, nothing's perfect. I wonder what the other four exceptions are? I bet you can't turn anything into a human. What else?
16) Much of the DA is there. And I've even started having respect for Lavender Brown. I bet all of these kids have matured a lot this year. And I bet a lot of wartime romances have been going on in this room. Pairings galore! But I bet I'm the only one who would pair Ernie and Luna. :p
17) Voldemort knows the ring is gone. Harry would be totally screwed without VoldieCam, wouldn't he?
18) You say you want a revolution.... They kids are ready to move, but the trio still have work to do, and then Harry's planning to leave again. Why? Eventually Voldemort has to come to Hogwarts, and they need to destroy Nagini as well. I suppose it's probably because they don't have the sword anymore. I guess it's going to be up to General Longbottom. Neville promised to summon Luna and Ginny if Harry showed up.
19) Luna and Dean arrive. And the Dean/Seamus 'shippers get their best moment this entire series. Luna is her usual upbeat but understated self.
20) How do Luna and Ginny and the other young ones get there? Everyone else is Apparating into the Hog's Head, but some of these kids are underage still, which should mean that A) they haven't had Apparition training and are therefore risking getting splinched, and B) the Ministry will be able to track them. But I guess Luna could have done side-along with Dean (wait; he can't Apparate without a wand, can he?), and Ginny with the twins .... That still doesn't explain how Muggleborn Colin Creevey got himself there in time, and he can't have been there all along, since they weren't letting Muggleborns into school this year.
21) Ginny the hottie. "He had forgotten, or had never fully appreciated, how beautiful she was." I've been paying attention on this read; this is the first time Harry has specifically thought of Ginny as being beautiful. The only one who have referred to her as such before now were Pansy (HBP on the train) and Krum at the wedding.
22) Cho shows up. She was watching her Galleon, apparently. Sounds like she's still a bit into Harry (probably because she likes attractive, heroic types). She wants to take Harry up to Ravenclaw tower and make out with him. But Ginny notices and doesn't trust her with Harry. She sends Harry off with Luna instead.
23) Ron says people can help *without* knowing what they're doing. He's right, too. Hermione agrees. These people trust Harry, and they'll follow his orders, knowing that he's got a mission straight from Dumbledore. Harry decides to place his trust in his friends and supporters.
24) The diadem vanished with Rowena Ravenclaw. Wait ... she vanished? According to Jo, she died of a broken heart for Reasons Unspecified. Anyway, the diadem hasn't been seen in a thousand years. However, there's a representation of it on Ravenclaw's statue in their common room. How handy!
25) Up until this book, Ravenclaw has been the most mysterious house at Hogwarts. And now we know why; almost anything Jo could have told us would be spoilerish.
26) The exit to the Room comes out somewhere different every time now. But to get back in, they still have to go to the seventh floor, right? Because otherwise, that would be really inconvenient.
27) Ravenclaw Tower. The Ravenclaw dorms are entered by answering riddles. The answers are apparently not told to the students like the Gryffindor passwords, but must be suggested by the students themselves. That doesn't seem quite as secure as the Gryffindor dorms; anyone who could answer the riddle could get in, and if even first year Ravenclaws can manage it, plenty of other people can as well.
28) "Wit beyond measure is man's greatest treasure." I'm guessing the answer to this is going to be "it's magic", but I'll ask anyway. Rowena Ravenclaw lived in the tenth century, and her diadem has not been seen since that time. Presumably this statue was made while she was alive, if it is an accurate representation of her and of the diadem. So why the f*** is the proverb on it written in modern English?! Sorry; my inner linguistics/history geek got away from me again.
29) Alecto was waiting. Her hiding place is more or less proof that Harry's guessed right about the final Horcrux. Why else would she be lying in wait beside that statue? We're supposed to think the real diadem is nearby, aren't we? How long has she been there, and what alerted her? Now she's gone and summoned Voldemort. Bugger.
Oh, and the hour later posting makes all the difference in the world! It means I have an extra hour after work to work on my posts, so I should get better about commenting on time! :p