Like the question of who Hermione loves is at the heart of debate on nearly all shipper sites, this question begs to be answered as well. It is every bit as important as the question of who does Hermione loves and it seems to be much harder to prove given that JK has only had Harry show blatant feeling for one girl, Cho Chang. So let's examine this for a moment.
How do boys usually show their feelings for a girl? Cruelty, if they're very young, but Harry has never really been cruel to Hermione, even when they were in their first year. Sure, he was a bit mean to her in the Sorcerer's Stone, as was Ron, but I don't believe that was an illustration of unconscious romantic love for Hermione on Harry's part. I think that at eleven years old, romantic love is still just a bit 'yucky'.
However, at fifteen, boys do feel romantic love for girls, and vice versa. I do believe that girls develop faster in this regard than boys do, and I believe Hermione came to realize her romantic feelings for Harry back in GoF.
Harry, however, has remained largely clueless about the concept of falling in love with a girl who has always been his best friend. I think that he began to wake up in Order of the Phoenix, however, and I think JK was clueing us in on these developments in Harry's feelings toward Hermione in many ways, such as Harry depending on Hermione for the most important tasks, for always trusting Hermione's council, and for the fact that Hermione is now, literally, the voice of Harry's conscience. My favorite clues as to Harry’s feelings for Hermione however, come in the form of Harry being extremely concerned about what Hermione thinks of him.
In the Order of the Phoenix, unlike in any other book of the series so far, Harry is deeply concerned with Hermione's opinion of him. He cares, like never before, what she thinks of him. I take this to mean that Harry is falling for Hermione; he just hasn't consciously admitted it to himself yet.
Some could argue that Harry only cares about Hermione's opinion because she's his friend. I disagree as far as the H/Hr relationship goes. Ron is Harry's friend, but he doesn't have moments about being concerned of what Ron thinks of him as he does with Hermione. Also, he doesn't seem to particularly care what Ginny or anyone else thinks of him either. However, there is one other person Harry wishes to impress in OOTP, and that's Cho Chang. If you take into consideration that the one person Harry truly wants to please is the object of his affection, Cho Chang, and then he behaves the same way (albeit unconsciously) with one other girl, Hermione (not Ginny, or any other girl in the series), you have to admit that this bears some serious thought that maybe, just maybe, that's because he's falling for her, or at least opening his heart to the possibility.
Harry is consciously aware that he has romantic feelings for Cho, and he cares what she thinks about him. Looking back at the train scene where Neville’s plant squirts stinksap all over the cabin, he was deeply embarrassed about looking bad in front of Cho. Was he embarrassed in front of Ginny and Luna? No.
Another thing that strikes me about Harry's feelings regarding Hermione in book five is how much Harry thinks of Hermione when she's not even in the room. No other girl takes up time and space in Harry's mind/heart unless they're actually in front of him, BUT Hermione. She's there in his mind, even when she's not there in body, and that's important.
Let us now take a look at some moments in OOTP where Harry is conscious of what Hermione thinks of him. Note, these thoughts aren't overtly romantic in nature, but they are very telling of feelings of love that Harry has for Hermione, and I believe these feelings go beyond friendship, and will someday develop into romance. If they don't, I have to admit that I will be deeply shocked. I can't imagine JK writing the perfect girl for Harry in Hermione and then pairing her with someone else.
Let's examine these quotes.
1-Only the house-elf's attitude of creeping servility looked convincing. With a grin at the thought of what Hermione would say if she could see the statue of the elf, Harry turned his money bag upside down and emptied not just ten Galleons, but the whole contents into the pool at the statues' feet.
It seems innocent enough, and really, it is innocent. Harry has just been cleared of charges that could have gotten him expelled from school, and maybe even imprisoned in Azkaban. He sees a house-elf and his friend comes into his mind. Funny though, that it was Hermione and not Ron or Ginny, or any other friend Harry has that comes to mind.
2- He dashed from the room, leaving Harry and Hermione alone. For some reason, Harry found that he did not want to look at Hermione.
Harry, as well as Hermione and everyone else for that matter, had taken it for granted that in fifth year Harry would be named Prefect. When that didn't happen, Harry, as well as everyone else, was shocked. What is interesting to me here is the wording Jo uses to describe Harry's feelings. For some reason, Harry found he did not want to look at Hermione. I don't think he would have had a problem looking at anyone else (he certainly doesn't feel this way when he next sees Ron, Ginny, Fred, George, or anyone else, just Hermione). He doesn't understand what he's feeling, because the idea that he is even allowed to fall in love with Hermione hasn't crossed his mind, yet I believe this is what is going on. He thinks he's looking bad in front of her, and that's humiliating to him. The reason for this still eludes him.
3-He (Harry) imagined trying to conceal from Hermione that he had received T's in all his O.W.L.s and immediately resolved to work harder from now on.
Harry couldn't give a flying hoot what Ron would think if he got T's in his O.W.L.s. Well, maybe he would care, but not to the extent that he cares what Hermione thinks. It's easy to realize that whenever Harry feels self-conscious about looking poorly in front of anyone it's always Hermione (or his almost-girlfriend Cho), never Ron (who is also his best friend), never Ginny (who is supposedly the "only" girl for Harry). Note here that it is his desire to look good for Hermione, to make Hermione think highly of him, that Harry resolves to work harder. This is love that goes beyond mere friendship in my opinion.
4-...he was halfway out of his seat, intending to hurry upstairs for his Invisibility Cloak when, not for the first time, a voice very much like Hermione's whispered in his ear: reckless.
This is one of my favorite quotes from OOTP, with the exception of the light-headed with relief part in the DoM. Jo is stating FLAT-OUT that Hermione is Harry's CONSCIENCE! This is the second time that she's been on his mind when she wasn't around, and it's always been a positive experience for Harry (the fountain scene at the MOM for Harry's trial).
Not for the first time...how long has this been going on? :D
Also note that Harry listens to the voice that's very much like Hermione's, and decides against doing something reckless. This is a very telling (almost profound) moment to me, because we all know that Harry has never been one to shy away from being reckless, bending, or even breaking the rules. However, his voice of reason (which has Hermione's voice) sways him from doing something stupid. This tells me that he obeys that voice out of a desire not to disappoint Hermione. Let me reiterate that he doesn't do it for Ron, or anyone else, but Hermione. At 15 years of age a boy doesn't usually behave this way for a girl unless he's motivated by deep respect and what? Say it with me people...LOVE.
5- ...though he wished he had not mixed up the incantations for Color-Change and Growth Charms, so that the rat he was supposed to be turning orange swelled shockingly and was the size of a badger before Harry could rectify his mistake. He was glad Hermione had not been in the Hall at the time and neglected to mention it to her afterward. He could tell Ron, though...
This is another favorite moment of mine, though not to the extent of the passage above. Harry made a blunder and he was relieved Hermione wasn't there to see him screw up, and on top of that, he made sure he didn't tell her about it afterward. He doesn't want to look bad in front of Hermione because he cares what she thinks of him, not just as a person, or a best friend, but as a GUY. Note that Harry doesn't have an issue with telling Ron of his mistake, but he does have an issue of telling Hermione. Some would argue because he wouldn't want to hear a lecture from Hermione on making mistakes during something as important as an O.W.L. exam, but if that were the case, I'm sure Jo would have written that (it would be easy enough to do) out.
There are more quotes in OOTP that support the H/Hr ship, but the above are the ones that strike me the most on just how much Harry cares for Hermione's opinion, and just how much he wants to impress her and look good for her. What really strikes me is how with the exception of Cho Chang (and those moments are when he's actually with her or looking at her), no other girl has such an impact on Harry's mind and feelings than Hermione. What does this tell you? It should tell you that not only are they best friends, but that they would make the perfect couple. Hermione is the perfect love for Harry, just as Harry is the perfect love for her. Who else knows Harry like Hermione? Who stands beside him like Hermione? Who gives Harry what he needs emotionally throughout the books quite like Hermione? Who else will STAND UP TO HARRY when he needs someone to step back and say "no" to him instead of bowing down to his temper to please him? No one but Hermione. And who really understands Hermione like Harry? No one. At the end of OOTP Harry knew that Cho Chang wasn't the girl for him. I truly believe that he will soon see who the girl for him IS in the next book. To me that girl can only be Hermione.
So...Who does Harry love?
I'm inclined to believe he loves Hermione.