The answer to this question depends on if you are referring to consequences in the negative sense, positive sense, or both. Typically, many regard a consequence as being something as negative, but this is not the case. A consequence is simply the result of an action.
This being said, there are many consequences in the novel To Kill a Mockingbird.
Given that Bob Ewell is a racist, the ultimate consequence that he faces for his own ignorance and prejudice is his death. If Ewell would not have been angry with Atticus and gone after the children, Boo would not have had to protect the children which resulted in Bob's death.
Another consequence in the novel is that both Scout and Jem see their father as a different person based upon his actions regarding the ignorance and prejudice he is forced to face as a result of taking on Tom Robinson's case. In the following quote, Atticus explains to the children about looking at a person for who they are, not what color they are:
"You never really understand a person until you consider things from his point of view - until you climb into his skin and walk around in it."
Well the most obvious consequence of ignorance and prejudice is racism which eventually leads to the tragic death of Tom Robinson.