Anglo-Saxon.net: Anglo-Saxon history traditionally starts with Hengest and Horsa and their three ships invading Britain in the mid-fifth century, and ends with King Harold falling with an arrow in his eye in 1066. These pages fill in some gaps.
The Avalon Project is a digital library of documents relating to law, history and diplomacy.
Germanic Lexicon Project: This site is a collection of digitized texts related to the early Germanic languages. The copyright has expired on all of these texts, and you may download them and use them however you please.
Medieval and Anglo Saxon Recipes: All from The British Museum Cookbook by Michelle Berriedale-Johnson, 1987, British Museum Publications.
EEBO includes facsimile pages of important works by literary giants like Chaucer and Bacon, but also contains many rare and little-known materials that were previously only available to those with access to special collections at academic libraries. Previously, the texts were only available to users at academic libraries involved in the partnership but the data was released into the public domain on 1 January, 2015.
This project was initiated at the 33rd International Congress on Medieval Studies by Larry D. Benson, Edwin Duncan, and Joseph Wittig, joined by a number of other medievalists. You can find information about the cohort of participants under Contributors. It contains links to Chaucer resources on the web collected by scholars.
The John Milton Reading Room: the complete poetry and selected prose of John Milton, with introductions, research guides, and hyperlinked annotations from Dartmouth College. If you are looking for something else, check The Culture Club's list of resources