Internet Medieval Sourcebook
Although the Medieval Sourcebook has now become a part of ORB (the Online Reference Book for Medieval Studies), it is often treated separately and still deserves its own listing. It contains thousands of primary documents from the Middle Ages (excerpts and full texts), as well as maps, secondary sources, links to course syllabi, and links to other academic resource sites. There are special sections for "Saints Lives," "Medieval Legal History," etc. The site is searchable.
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Erin Littlepage (Faculty)
Excellent resource for primary and secondary source materials.
Kimberly Dyer (Faculty)
I have used this site many times in my own research and have also brought it into the classroom. The Internet Medieval Sourcebook is a one stop shop for many popular primary and secondary sources that students can use in their research. My only complaint with the site is that it can be a bit difficult/cumbersome to navigate for some students.
No special software is required to use this site, and it is accessible on smart phones/iPads.