Over at Crossway, they've made Greg Forster's book "The Joy of Calvinism" available for FREE download:
At Ligonier, along with the Mystery of the Trinity special I mentioned the other day, they are offering R.C. Sproul's "Luther and the Reformation" series for FREE download (MP3 & MP4) as well:
Desiring God has FREE digital downloads of John Piper's biographical sketch entitled,"Martin Luther: Lessons from His Life and Labor":
More Reformation resources:
Don't forget to check out the various pages on this blog... there are some great Reformation resources in the "Historical Theology" section as well as a number of classic and contemporary Reformed/Evangelical articles on the other pages.