There are many opposing forces that can be pitted against each other in Act Three of the "The Crucible." One, that you mentioned above, is a big one--lies versus truth. Abigail is the main force for telling lies in this play, and in this act. She lies about Mary being a bird, lies about the affair with Proctor, and lies that she was not faking all of the tribulations of the trials. Also, Elizabeth Proctor tells the first lie of her life in denying that her husband was a lechery. Also look at Mary Warren, who tried telling the truth, but in the end caves to the power of the lie. Contrast these lies to Proctor and his unvarying truth-telling. He insists that Mary has told him that the girls are faking it. He tells the truth about Abby, even if it cost him his reputation. In the truth versus lies battle, lies win. The courts disbelieve Proctor, and believe instead Abby, leading to Proctor's arrest.
Other contrasting themes in this act can be seen in power and pride versus humility. Danforth, Hathorne and Parris demonstrate naked pride and power-grubbing. They claim to be the "high court," "officials of the court," and that no god-loving citizen should fear them because of their almighty ability to discern truth. Their word stands above all, and instead of listening to reason, sanity or honest people's witnesses, they get defensive, arrest everyone, and protect their precious power and previously made judgments. Contrast that with the humility of several farmers--John, Giles and Francis--who come to the courts in a desperate attempt to save their wives. They do not know the law, they don't have lawyers to protect them, and yet they come anyway, trusting truth to be on their side. Unfortunately, in this battle, pride and power wins out over humility.
One other contrast is logic versus chaos and confusion. What makes more sense, that spirits are floating about afflicting people, stabbing them with needles, or that Abby wants to hurt Liz for embarrassing her, and to be with John? What makes more sense, that a yellow bird has come to claw out Abby's eyes, or that Abby is afraid of being discredited? What makes more sense? That 98 people signed a petition because the people arrested are GOOD people, or that Satan somehow influenced nearly 100 people to falsely sign their names? All of these examples demonstrate the insanity of the courts and what they believed. Logic lost every single time.
I hope that those thoughts helped; good luck!