Edwin
Duncan's Internet Resources (Towson University): A broad selection
of useful links to sites with information on medieval literature and
history.
Cathy
Ball's Old English Pages (Georgetown University): A good set of
resources for the study of Old English literature and Anglo-Saxon
culture.
The Harvard
Chaucer Web Site: A site dedicated to Chaucer, but with many items
of general interest for the study of late medieval English culture.
See also The Chaucer Meta Page for a similar range of materials.