John Piper online

I recently came upon an excellent resource for Christians wanting to heighten their theological and Scriptural knowledge. Famed theologian and pastor, John Piper has virtually all of his books, sermons, etc. online at his ministry website: www.desiringgod.org.

Note that you aren't required to purchase these items. You can simply read his books in PDF format directly on the site. This is a treasure trove and shouldn't be missed.