I cannot recommend this highly enough.
It is a series of lectures given recently by Father Andrew Damick of
St George Cathedral in Charleston, WV on the many differences (and a few similarities) between Orthodox Christianity and the many other religions--Christian and otherwise--that are out there.
It is a fascinating and thorough and fair examination of the history and core beliefs of these religions and I strongly suggest that you take the time to listen.
Clicking on each title below will link directly to the audio file. They take a little while to download (each lecture is over an hour long), but, believe me, it's worth it.
Lecture 1:
Heterodoxy & Heresy (series introduction)
Lecture 2:
Roman CatholicismLecture 3:
Churches of the Classical Reformation (Lutherans, Calvinists, Reformed, Zwinglians, Anglicans, Episcopalians, Methodists, Wesleyans)
Lecture 4:
Churches of the Radical Reformation (Anabaptists, Baptists, Brethren, Amish, Mennonites, Restorationists, Adventists)
Lecture 5:
Modern Revivalism (Pentecostalism, Charismatics, Evangelicalism)
Lecture 6:
Non-Christian Religions (Judaism, Islam, Buddhism, Hinduism, Shinto, Sikhism, Wicca, Neo-paganism, Zoroastrianism, Modern Gnosticism, Animism)
Lecture 7:
Non-Mainstream Christians (Swedenborgians, Mormons, Jehovah's Witnesses, Unitarian Universalists, Christadelphians, Christian Science, Unification Church ("Moonies"); also includes series conclusions)
From Christ in the Mountains by Fr. Andrew Damick