Here is a link to a good commentary on the atonement by Mark Dever:
Dever does a good job of defending penal substitution while affirming the other great things Jesus acheived on the cross (like triumphing over the powers and blazing a trail for his disciples to follow).
In this he follows Paul, who could speak of Jesus's death atoning for our sins and triumphing over the powers in successive breaths:
"And you, who were dead in your trespasses and the uncircumcision of your flesh, God made alive together with him, having forgiven us all our trespasses, by canceling the record of debt that stood against us with its legal demands. This he set aside, nailing it to the cross. He disarmed the rulers and authorities and put them to open shame, by triumphing over them in him (or: "in it"--i.e. in the cross)."
Colossians 2:13-15 (ESV)