In addition the ATLA database and other general religion/theology databases, you may find the following databases helpful:
Manchester Medieval Sources OnlineManchester Medieval Sources Online contains hundreds of original medieval history documents compiled for the teaching and study of history. Includes both translations of source documents and thematic volumes. Provides access to the Medievalportal, which provides a gateway to other medieval material on the Internet.
International Medieval Bibliography (IMB)IMB (International Medieval Bibliography) indexes articles in journals, Festschriften, conference proceedings, and collected essays, covering all aspects of medieval studies within the period 450 to 1500 for Europe, the Middle East and North Africa. Date coverage: 1967 - present.