In the Pines Pantry, Keegan is shown holding a carrot in his hand just after having put the carrot under his shirt.
Toward the end when Will is seen ducking into the Ice Palace walkway, Noah is seen approaching from the right. In the shot immediately preceding, he was far from the Ice Palace walkway on what would be the left of the subsequent shot.
The film shows the group watching a sunset over the Atlantic Ocean...the sun RISES over the Atlantic Ocean and SETS over the Pacific.
Edit: While this is true, the sun does set over Great South Bay from the perspective of the island, so not a goof.
On Sunday, Will is seen eating an ice cream cone in Cherry Grove and ducking into the Ice Palace. It's implied that Noah is there soon after having left his Pines house. Cherry Grove is a distance from the Pines, and an earlier scene also mentions that the journey is either by water taxi or a long way by foot.