There are a number of complete translations of Beowulf on-line. Project Gutenberg (http://gutenberg.org) features three: William Morris and A.J. Wyatt, Francis Barton Gummere, and Lesslie Hall. It has, as well, the Old English version edited by Harrison and Sharp and a useful critique of early translations by Chauncey Brewster Tinker.
Of these, Gummere's 1910 translation is best, possibly because he developed it for oral reading in a classroom. It keeps the poem's form and follows its meaning quite closely. However, tastes in poetry have changed, and Gummere uses a poetic diction that is no longer in style. Unfortunately, Morris's version is unreadably archaic in language. Hall's is a freer translation than those two, and does not follow the original line for line.
For a literal translation, side by side with the original Old English, and with copious notes, a wonderful resource is Ben Slade's site (http://heorot.dk). I've leaned on this heavily.
Another wonderful site, Beowulf Translations (http://beowulftranslations.net/) is scheduled to disappear from the Internet on 31 December 2011. This site has selections from many, many translations of Beowulf for comparison. Anyone who can should take advantage of Syd Allen's offer and download the entire site as a zip file.
The Klaeber edition of Beowulf has been the standard Old English edition for decades. It is on-line, though without the copious notes in the book, at this site: http://www.fordham.edu/halsall/basis/beowulf-oe.html.
An on-line magazine called January Magazine has selections from the translation of Beowulf by Charles W. Kennedy, originally published by Oxford University Press. I had not seen this alliterative verse translation before. It is modern and readable. The January Magazine article also has a link to the full text of the book on the Questia Online Library. Questia is a paid service, though, so only part of the introduction and the first page of the poem are there for free. For now, at least, you can find much of it also here.
Kennedy's introduction to Beowulf has an annoying oversight, though. He says, "THE Old English Beowulf holds a unique place as the oldest epic narrative in any modern European tongue." Isn't Greek "a modern European tongue"? So shouldn't that honour go to The Iliad or The Odyssey?
Another free one is here. It is by Dick Ringler and is titled Beowulf: A New Translation for Oral Delivery. It is dated May, 2005.
It is the nature of the Internet that resources appear and disappear. I don't expect the Project Gutenberg books to disappear: that organization is not going away soon, if at all, but the others may be ephemeral. Still, what disappears in one place may reappear in another, so do not let a dead link stop you from searching further.