Pearl: Another symbol for Hester's sin and is the living version of the scarlet letter on Hester's chest. This is shown when Pearl won't come back to her mother unless she is wearing the A on her chest.
The sun: A symbol for freedom and purity, this is because it shines on Hester only when she throws off the scarlet letter while she is in the forest. Pearl also mentions how the sun hides from Hester because of the A on her chest but not from herself because she does not have one and is a pure child.
The forest: At first the forest is a symbol for hell, this is why Hester lives in between the Forest and the town. In chapter 17 Hester is with Dimmesdale in the forest and tells him about Chillingworth, somewhat freeing herself from sin. She throws her scarlet letter off showing how she no longer feels the need to carry the burden of her sin, now the forest is viewed as a magical place instead of hell.