Although Golding seems to be commenting on the worst of human behavior in the novel, there are some examples of positive behavior. The author posits that without the restraints and expectations of normal society, humans devolve into their basest nature. So without the influence of school, teachers, parents, police, etc., the boys might descend into savagery, but there are a few notable examples.
The most prominent is probably Simon. He helps wherever he is needed by building shelters or tending to the little boys. He even has an almost holy nature. At times he leaves the other boys to sit in a calm spot in the forest in order to think/meditate.
Piggy also shows positive traits. He's smart and tries to use his intelligence to guide the boys. He tries to keep track of the smaller boys and thinks it's a good idea to take down their names. His glasses are used to start fires which could lead to rescue. Although he's weak and socially awkward, he is never malicious in any way, so he is a sympathetic character.
Ralph also has good characteristics. In the beginning, he is friendly with Jack and even sides with Jack against Piggy, but as time passes, he becomes concerned with being a good leader and what's best for the whole group. He tries to focus on the fire and rescue although he is sometimes caught up in the fun and violence of Jack and his tribe.