TruthWillPrevail.org has put together a wonderful and enlightening 5 part series on Mormon Plural Marriage which we would like to share here:
Part 1: Scriptural Support for Plural Marriage: The Old Testament
Part 2: Scriptural Support for Plural Marriage: The New Testament
Part 3: Doctrinal Basis for Modern Plural Marriage
Part 4: Reluctance of Early Mormon Leaders to Take Plural Wives
Part 5: Testimonies of Plural Wives