If you are looking for some great free resources, or just plain good resources period, I highly reccomend you visit:
You will find numerous free pdf books: Apologetics, Theology, and Bible Commentaries.
Here is more information about him and his aims (from his site):
About Vincent Cheung
Vincent Cheung is the author of over thirty books as well as hundreds of lectures and sermons on a wide range of topics. Among his publications are foundational texts in Christian theology, philosophy, apologetics, spirituality, and a number of biblical commentaries. He is committed to the inspiration and inerrancy of Scripture, and thus all the doctrines that it affirms — that God is sovereign over all things and all minds, that the non-Christian man is unrighteous and unintelligent, that Jesus Christ is the only way to salvation, that the believer possesses eternal life and would be received into heaven, and that the unbeliever is condemned to everlasting suffering in hellfire. Through his outreaches and publications, he is training Christians to understand, implement, and advance the biblical worldview as a comprehensive and coherent system of thought revealed by God in Scripture. He and his wife, Denise, reside in Boston, Massachusetts.
Message to Readers
As the online extension of my ministry, this web site exists to promote Christianity as it is revealed in Scripture, and as it is systematically expressed in various statements of Reformation theology such as The Westminster Confession, The Belgic Confession, The Heidelberg Catechism, and The Canons of Dordt. It achieves this purpose by distributing my growing library of writings free of charge and in an accessible format.
My Systematic Theology is the main text on Christian doctrines, and Ultimate Questions is my text on Christian philosophy. Then, I further explain my theology, philosophy, and approach to apologetics and its biblical basis in Presuppositional Confrontations. This work includes an extensive exposition on Paul’s Areopagus discourse as recorded in Acts 17. The short work, Apologetics in Conversation, introduces several important principles for informal debates. My answer to “The Problem of Evil” appears in The Author of Sin, which also includes some polemical articles related to the doctrine of divine sovereignty.
The Sermon on the Mount provides an introductory exposition of biblical law and ethics. Prayer and Revelation is an introduction to biblical spirituality and prayer. My thoughts on homiletical and educational principles are stated in The Ministry of the Word, which also includes a detailed discussion on the inspiration and inerrancy of Scripture.
In addition to these texts, my writings include biblical commentaries, topical studies, and lessons in reasoning and argumentation. My intention is to construct a body of works to cover a wide spectrum of Christian concerns. Please browse the online library to view the list of available publications and their descriptions.
Thank you for visiting this web site, and for your prayer and support.