(From a liberal Christian netfriend):

Soul Survivor (How my faith survived the Church) - Philip Yancey

The Varieties of Religious Experience - William James

Letters and Papers From Prison - Dietrich Bonhoeffer

Fit Bodies, Fat Minds (Why Evangelicals don't think and what to do about it) - Os Guinness

On Being A Christian - Hans Kung

A History of God - Karen Armstrong

A History of Israel - John Bright

Stages of Faith - James W Fowler

Honest to God - John T Robinson

Rescuing The Bible From Fundamentalism - John Shelby Spong

A New Christianity For A New World (Why traditional faith is dying and how a new faith is being born) - John Shelby Spong