Calvinist website Desiring God is offing 14 free books.

Adoniram Judson: How Few There Are Who Die So Hard!
Alive to Wonder: Celebrating the Influence of C. S. Lewis
Andrew Fuller: I Will Go Down If You Will Hold the Rope!
David Brainerd May I Never Loiter On My Heavenly Journey!
Disability and the Sovereign Goodness of God
Doctrine Matters: Ten Theological Trademarks from a Lifetime of Preaching
Good News of Great Joy: Daily Readings for Advent
John G. Paton: You Will Be Eaten By Cannibals!
Love to the Uttermost: Devotional Readings for Holy Week
Martin Luther: Lessons from His Life and Labor
Preparing for Marriage: Help for Christian Couples
Sanctification in the Everyday: Three Sermons by John Piper
Take Care How You Listen: Sermons by John Piper on Receiving the Word
A Tribute to My Father: With Other Writings
An All-Consuming Passion for Jesus: Appeals to the Rising Generation
Captive to Glory: Celebrating the Vision and Influence of Jonathan Edwards

For pdfs and descriptions, click here.