and "for some reason, Darry seems to like being teased by Soda" (Hinton 9).  Sodapop's intuition and loving spirit helps hold his family together; he actively works on nurturing and encouraging each of his brothers in the was that best suits them.

Soda, the middle of the Curtis brothers, generally has a positive effect on other characters. He is laid-back, handsome, friendly and cheerful, and therefore gets on well with people. In a word, he is charismatic.

Soda's most important relationships, though, are with his two brothers. He is more open and easygoing than either of them - Darry, the eldest is serious, always conscious of his responsibilities, while Ponyboy, the youngest, is rather nervous and unsure. The two of them continually spar with one another, with Darry trying to instill a sense of maturity into Ponyboy and Ponyboy resenting what he feels are Darry's heavy-handed ways.

Soda is caught between his two brothers and has to play the role of mediator; therefore he is the middle brother in more than one sense. It is not until near the end of the book that the other two realize what a strain this puts on Soda. Because he always seems cheerful, other people generally assume that he hasn't got any problems, but he finally breaks down and runs away from his brothers when they're having yet another quarrel. He confesses that how badly it affects him, being caught in the middle all the time. The revelation shocks and even 'shames' Ponyboy:

Neither of us had realized what it was doing to Soda to hear us fight. I was sick and cold with shame. What he said was the truth. Darry and I did play tug of war with him, with never a thought to how much it was hurting him.

Soda, then, acts as peacemaker and mediator. He is part of the Greasers' gang like his brothers but generally he is not into any kind of conflict. He is very generous in spirit towards other people, but that doesn't mean he hasn't problems of his own. We only really see his emotional vulnerability at the end of the book (when he also loses his girlfriend Sandy). Ponyboy simply idolizes him but also has to come to a more mature understanding of him - as, indeed, does Darry. When they both realize how much they've been hurting Soda, it has the effect of bringing the three brothers closer than they've ever been. 

I think the other answers to this question are great, and I definitely agree with them.  I also think Ponyboy Curtis can be considered a hero in S.E. Hinton's The Outsiders, because he is a survivor.  Losing both parents at a young age is incredibly hard on a child, but Ponyboy and his brothers are able to make it on their own, even if it's by just barely getting by every month.  I also have a tremendous amount of respect for Ponyboy because he knows the value of education.  He is a dedicated student and a hard worker.  Most kids would have just given up, thinking their futures futile if they had no money and no parents.  Ponyboy, however, continues to work hard and do well, with the hope of receiving a college scholarship.  He could have very easily gone the other way and decided school wasn't for him.  Instead, though, he makes the wiser decision to stay in school and do well.

I would say Pony is a hero in two ways.  He is a hero in the conventional sense for helping to save the kids and he is a hero in a less conventional sense for overcoming his problems.

We usually think of heroes as people who rescue other people or do something equally brave.  Pony did this, and so he is a hero in that way.

But to me, a hero is also just someone we can or should admire.  And I think we should admire Pony for overcoming all the problems he has and the temptations to become a bad person.  I think Pony is admirable because he is going to "stay gold."