Another way that Huck grows throughout the novel is in his views on society and being 'civilized'. At the beginning of the novel, Huck's objections to society revolve mainly around things like having to dress properly, going to school, having to stay clean, and being proper. These things are fairly superficial, and his objections are simply the personal preferences of a pre-teen boy. As the novel progresses, however, Huck is exposed to some very difficult circumstances, and his views of society grow and mature as a result.
Huck watches as Sherburn shoots Boggs, and he listens to Sherburns speech about how cowardly most of society is. He sits in a tree and becomes nauseous as he watches the Sheperdsons kill off the Grangerford clan, including his young friend Buck. And Huck observes as over and over the King and the Duke manipulate and con innocent, naive members of society. As the King and Duke are tarred, feathered, and rode out on a rail, Huck declares that people sure can be cruel to each other. Throughout all of these experiences, Huck matures from a boy who despises being 'civilized' simply because he doesn't want to have to keep clean to a young boy who makes some very mature decisions about what is right and wrong in the society around him.
The most obvious way that Huck matures emotionally is through his relationship with Jim. Huck, being a southerner, grew up "knowing" that black people were slaves and worthy only of such menial labor. Slaves were not deemed intelligent (since they weren't offered education on a wide scale) and were considered less than whites. On his journey with Jim, Huck recognizes Jim as a person with goals, feelings, loyalties, and morals. When Jim saves Huck's life, Huck's view of Jim and his place in the world as Huck has come to understand it is all skewed. Huck becomes confused and finally decides what he has learned is not correct. He begins to follow his own path and to reconsider his lessons of the black/white issue. Jim has become his friend--a person to care for and to comfort--he is no longer "just a slave" to Huck. Emotionally, this is a huge step toward becoming a man and thinking things through for himself rather than just following traditional lines of thought.
This voyage provided a great possiblity for Huck to experience life outside of basic stereotypes. His biggest transformation can be seen through his relationship and interaction with Jim.
In the beginning, he and Tom find fun in pranking on Jim. They view him as an ignorant and simple slave who is strictly property that can be played with.
Throughout the course of the novel, Huck battles a strong internal conflict between Jim as a friend and Jim as property. He has been taught by society that the correct and prudent thing to do would be to turn Jim in (he actually feels like he is stealing from the Widow); however, Huck recognizes Jim as a true friend and is hesitant to rat on a friend. These feelings are further complicated by Jim's talking about buying his wife and freeing his children if he becomes free. Huck questions whether or not he wants to be a part of stealing from people he's never met.
By the end, Huck seems to have accepted Jim as a person. He refers to Jim as the whitest n- he's knows (as close to a compliment as could be expected), he made the decision to help Tom free Jim, and is in awe when Jim sacrifices his freedom to help Tom after Tom was shot.
That's not to say Huck was completely changed though, as he is all set to run away again to avoid the newest attempt to civilize him!