1. In chapter eight, Jim confesses to Huck that he has "run off."  Though Huck is initially shocked, he agrees to listen to Jim without telling on him.  Huck reassures Jim that "people would call me a low down Ablitionist [sic] and despise me for keeping mum--but that don't make no difference." This exchange represents man v. society in two ways:  Jim has broken the law by escaping slavery, and Huck agrees to aid a fugitive, thereby also breaking the law.
2. Earlier in chapter eight, Huck watches in hiding as "most everybody" on the boat is looking for his body.  He hears the captain say "maybe he's washed ashore and got tangled amongst the brush at the water's edge. I hope so, anyway." Huck expresses the opposite view, thinking "I didn't hope so."  Huck doesn't want to be dead, but he also doesn't want to be found and returned to a society in which he does not feel at home.
3. When Huck meets Mrs. Loftus in chapter eleven, he listens to her talk of how she has sent her husband to Jackson's Island to look for the runaway slave.  Though she shows Huck some kindness, he does not agree with the idea of rounding up Jim for a reward, as she and her surrounding society do.

Just to add a little to the previous answer, the chapters do provide some images that demonstrate the man vs. society conflict as well.  

1.  When Huck is on the island, he watches the steamboat come by with everyone he knows on it looking for him.  This scene presents a visual representation of Huck vs. society - everyone is searching for him, but he chooses to watch from his hiding place on the island.

2.  Jim's recounting of his escape also provides an image of the man vs. society conflict.  It shows a human side of a slave - a slave struggling for his freedom vs. those who would call him an animal and keep him in captivity.

3.  Jim and Huck's flight at the end of chapter 11 is another example.  Both are going against society by fleeing and by being with the other. 

In chapters 8 and 9, Huck feels that being on the island, separated from society, has removed him from the conflict of dealing with the demands of others: “I wouldn’t want to be nowhere else but here.” Huck wants to escape the ridiculous fighting and prejudices and expectations society imposes.

However, he realizes that this oasis is unrealistic and that he must help Jim escape, even if people will call him a "low down abolitionist."

Things get stickier for Huck when he learns that people back home, first thinking Pap had killed Huck, now believe that Jim is the murderer. Huck must once again come into conflict with society by continuing to protect his friend. (chapters 9-11)