Updated January 24, 2016
A Google search on the word “Beowulf” yields approximately 10,400,000 results. I cannot claim to have visited them all, but I suspect that not all of these sites are equally useful to a reader of the poem. The internet is a vast and unruly place, and the quality and relevance of its information varies widely. All the sites here are recommended with confidence, but when you venture out into other sites, be sure to evaluate the content carefully before you use it as a reference. Advice on how to do this can be found at http://www.studygs.net/evaluate.htm and http://www.wiu.edu/users/mfbhl/evaluate.htm.
Each of these links will take you to more resources, including images of the manuscript, artifacts from Anglo-Saxon England, aids to language study, and even more links:
Aids for learning Old English
General Medieval Links
Beowulf: a household name?