Important Websites and Ministries:

The Threshold - A tremendous resource of Reformed material. 

Ligonier Ministries - The teaching ministry of Dr. R.C. Sproul

Desiring God Ministries - The ministry of Dr. John Piper

Alpha and Omega Ministries - Ministry headed by Dr. James White.

A Few Books (Listed alphabetically by author.  Click on title to go to a site offering the resource):

Reformed Dogmatics - Herman Bavinck

Systematic Theology - Louis Berkhof

Summary of Christian Doctrine - Louis Berkhof

The Discipline of Grace - Jerry Bridges 

Institutes of the Christian Religion - John Calvin

Calvin's Commentaries of the Bible - John Calvin

Christ-Centered Preaching - Brian Chapell 

Systematic Theology - Wayne Grudem 

Christianity in Crisis - Hank Hanegraaff 

Systematic Theology - Charles Hodge

Putting Amazing Back into Grace - Michael Horton

The Bondage of the Will - Martin Luther 

Redemption Accomplished and Applied - John Murray

The Battle Belongs to the Lord - K. Scott Oliphint

Reasons {for faith} - K. Scott Oliphint

Concise Theology - J.I. Packer

Evangelism and The Sovereignty of God - J.I. Packer

Knowing God - J.I. Packer

The Sovereignty of God -  A.W. Pink (click to read on-line) 

Desiring God - John Piper

The Passion of Jesus Christ - John Piper

Every Thought Captive - Richard Pratt

The Case for Amillennialism - Kim Riddlebarger

Biblical Preaching - Haddon Robinson 

Refuting Evolution - Jonathan Sarfati 

How Should We Then Live - Francis Schaeffer 

The Great Evangelical Disaster - Francis Schaeffer 

The God Who is There - Francis Schaeffer

History of The Christian Church - Philip Schaff

The Universe Next Door - James Sire 

Chosen By God - R.C. Sproul

The Holiness of God  - R.C. Sproul 

Biblical Theology:  Old and New Testaments - Geerhardus Vos

The Works of Benjamin Warfield - B.B. Warfield

The Forgotten Trinity - James White

The Potters Freedom - James White 

The Westminster Confession of Faith

For those interested in a great introduction to Calvinism, I heartily recommend this DVD:  Amazing Grace: The History & Theology of CALVINISM.  This is a 2 DVD set, and is extremely well done.  It is must viewing, especially for those with questions.