If we want to find examples of equality in Harper Lee's To Kill a Mockingbird, we will probably need to do some interpretive work. Certain instances of character, action and dialog in the novel lend themselves to interpretation as comments on human equality.
Approaching the novel in this way, we can see Tom Robinson's trial both as a negative example of inequality and of the positive value of equality.
While we can point to lines like this one -"I think there's just one kind of folks. Folks.” - we might more powerfully argue that the novel makes its greatest commentaries on equality in (1) its demonstration of racism at work in the legal system and (2) in Boo Radley's ultimate exoneration.
How does Tom's trial relate to equality? It is the trial that challenges the town's preconceived notions of race, racial superiority/inferiority, and presumed "white moral/legal authority."
"Atticus doesn’t kill racism in Maycomb county; he can’t. But by showing his children racism in action and fighting the prejudice of the “mockingbirds” of this stereotypical Southern town, Atticus plants the seeds of a future in which blacks and whites can live in peace" (eNotes).
How does Boo Radley's character ultimately relate to equality? Boo Radley is presumed to be wicked but is revealed to be meek, helpful and more fearful than fearsome. This revelation further demonstrates the novel's commentary on the tendency of prejudice to be false and, by extension, suggests that "people are people" regardless of rumor and regardless of race.
It's probably easier to point out the examples of inequality--the churches are segregated, the trial is segregated (whites downstairs, blacks up in the balcony) and the town is segregated geographically--whites live on one side and the blacks live on the other. The exception there is the Ewells who live near the dump next to the black part of town.
One example of equality is that Tom Robinson is given Atticus as a trial lawyer. This public defender title is usually given to the lawyer with the least experience so they can actually get experience. Atticus is chosen (or so it is implied in the book) because the judge believes Tom is innocent and deserves a better attorney than the most inexperienced on staff.
Another example of equality is when Atticus is explaining the use of the word "nigger-lover" to Scout. He does not differentiate between black and white...he simply says he does his best to love all God's people.
Atticus also refuses to fire Calpurnia just because Alexandria wanted her out of the house. Atticus loves Calpurnia as if she were a biological member of the household.