Leon Morris on The Atonement:

"The NT does not put forward a theory of atonement, but there are several indications of the principle on which atonement is effected. Thus sacrifice must be offered, not the sacrifice of animals, which cannot avail for men (Heb. 10:4), but the perfect sacrifice of Christ (Heb. 9:26; 10:5-10). Christ paid sin's due penalty (Rom. 3:25-26; 6:23; Gal. 3:13). He redeemed us (Eph. 1:7), paying the price that sets us free (I Cor. 6:20; Gal. 5:1). He made a new covenant (Heb. 9:15). He won the victory (I Cor. 15:55-57). He effected the propitiation that turns away the warth of God (Rom. 3:25), made the reconciliation that turns enemies into friends (Eph. 2:16). His love and his patient endurance of suffering set an example (I Pet. 2:21); we are to take up our cross (Luke 9:23). Salvation is many-sided. But however it is viewed, Christ has taken our place, doing for us what we could not do for ourselves. Our part is simply to respond in repentance, faith, and selfless living."

(taken from http://www.monergism.com/thethreshold/articles/onsite/atonementmorris.html)

"All the above views, in their own way, recognize that the atonement is vast and deep. There is nothing quite like it, and it must be understood in its own light. The plight of sinful man is disastrous, for the NT sees the sinner as lost, as suffering hell, as perishing, as cast into outer darkness, and more. An atonement that rectifies all this must necessarily be complex. So we need all the vivid concepts: redemption, propitiation, justification, and all the rest. And we need all the theories. Each draws attention to an important aspect of our salvation and we dare not surrender any. But we are small minded sinners and the atonement is great and vast. We should not expect that our theories will ever explain it fully. Even when we put them all together, we will no more than begin to comprehend a little of the vastness of God's saving deed."

(taken from http://www.monergism.com/thethreshold/articles/onsite/atonementmorris2.html)