Internet History Sourcebooks Project
Fordham University: Medieval Sourcebook: Inquisition
Article provides a detailed introduction to the inquisition as a legal proceeding rather than the Spanish relgio-secular institutional body that the word more often brings to mind.
University of Notre Dame
Notre Dame: The Inquisition Collection
This collection of more than 500 original documents from the Spanish Inquisition features the Holy Offices Manual of Instructions and the Index of Banned Books. The introductory information and notes are in English.
Other
Orthodox Press: The River of Fire
This keynote address from a 1980 Orthodox Youth Conference addresses the differences between eastern and western conceptions of Christianity. Includes detailed footnotes; very interesting.
Rice University
Galileo Project: Inquisition
The Galileo Project provides a broad overview of the Inquisition, a legal institution in the Catholic Church charged with the eradication of heresies.
Rice University
Galileo Project: Historical Overview of the Inquisition
This article defines an inquisition, which is a legal proceeding of the Catholic Church and not restricted to a particular institution such as the Spanish Inquisition.