Beowulf | Notes
Bosworth-Toller Dictionary is here.
Fontes Anglo-Saxonici is here (an on-line database of sources of Old English).
Wiley Blackwell Encyclopedia of Anglo-Saxon England is here (through UMass only).
Allen Frantzen, Anglo-Saxon Keywords, a guide to major topics in Old English studies (through UMass only).
Stewart Lee of Oxford has a site where he's invited the public to post websites.
And more seriously, a phenomenal on-line edition of a series of books called penitentials. These were handbooks used by priests to determine what kind of penance a person had to do. It shows you what the original, hand-written books looked like.
And a recently discovered hoard of treasure, the likes of which have never been seen before.
Benjamin Bagby doing his unique thing. Here are the first lines that Bagby sings (starting at about line 102 of Beowulf):
 Þone cwealm gewræc ece drihten, þæs þe he Abel slog; ne gefeah he þære fæhðe, ac he hine feor forwræc, metod for þy mane, mancynne fram.
 Þanon untydras ealle onwocon, eotenas ond ylfe ond orcneas, swylce gigantas, þa wið gode wunnon lange þrage; he him ðæs lean forgeald.
 Gewat ða neosian, syþðan niht becom, hean huses, hu hit Hringdene æfter beorþege gebun hæfdon.
 Fand þa ðær inne æþelinga gedriht swefan æfter symble; sorge ne cuðon, wonsceaft wera.
 Wiht unhælo, grim ond grædig, gearo sona wæs, reoc ond reþe, ond on ræste genam þritig þegna, þanon eft gewat huðe hremig to ham faran, mid þære wælfylle wica neosan.
 Ða wæs on uhtan mid ærdæge Grendles guðcræft gumum undyrne; þa wæs æfter wiste wop up ahafen, micel morgensweg.
And an example of (better) folk singing while plucking on strings (in this case, two violins).
Serious resource: Vladimir Orel, A Handbook of Germanic Etymology (free through UMass). A dictionary and more, arranged by proto-Germanic headword.
Roy Liuzza's collection of important essays on Old English (through UMass only)