Books:
The Pilgrim's Progress by John Bunyan
Matthew Henry’s Complete Bible Commentary
(provides an exhaustive look at every verse in the Bible)
Voices from the Past: Puritan Devotional Readings (Volumes 1 & 2)
(among the best devotionals available, alongside Spurgeon's Morning and Evening)
Studies on Saving Faith by A.W. Pink
(genuine conversion vs. false "conversion")
The Sovereignty of God by A.W. Pink
(preferably the unabridged Baker Book House edition)
The Attributes of God by A.W. Pink
Humility by Andrew Murray
Foxe’s Book of Martyrs by John Foxe (available for online reading at biblestudytools.com)
Dying Thoughts by Richard Baxter
The Book of Revelation Made Easy by Kenneth Gentry
Puritan Evangelism by Joel Beeke
Evolution at the Bar by Philip Mauro
(Explains why Darwin's theory cannot be true)
The Invitation System by Iain Murray
(against emotional appeals and "altar calls")
Home-Making by J.R. Miller
(sometimes published as The Family)
Far from Rome Near to God: Testimonies of Fifty Converted Roman Catholic Priests
50 Years in the “Church” of Rome: The Conversion of a Roman Catholic Priest
by Charles Chiniquy
“Truth in Depth presents Mormonism’s Greatest Problems” (Audiobook CD 3 Discs; a great resource, if you can find it. The true character of Joseph Smith was even worse than you had imagined.)
Websites:
9marks.org (church search)
founders.org (church search)
Monergism.com (salvation is all of God's grace)
apuritansmind.com
reformedreader.org
graceonlinelibrary.org
lds.video (a call to Mormons) https://lds.video/index.html
The American Vision americanvision.org
Bible commentaries:
Matthew Henry, John Gill, Geneva Bible notes; these may be found online at BibleStudyTools.com
YouTube searches:
"Racial Reconciliation - Ephesians 2:10-11 Dr. Voddie Baucham"
"Voddie Baucham - Cultural Marxism"
“Living Waters” & “Ray Comfort: Just Witnessing” channels
“Catholicism: Crisis of Faith”
“The Mormons: Who They Are, What They Believe”
“The God Makers: Mormonism Exposed”
“The Shocking Truth Behind Jehovah’s Witnesses” (“Living Waters” YouTube channel)
Miscellaneous:
“One Race, One Blood” (usually available for viewing on YouTube)
Authority in the Christian Life by Jean-Marc Berthoud
The Law by Frederic Bastiat
Walden by Henry David Thoreau