Of all the ancient Germanic languages, the largest corpus survives in Old Norse - the language of the Vikings - largely thanks to its preservation in medieval Iceland. Even today an Icelander can read Old Norse even more easily than a modern English speaker can read Chaucer.

Haukur Þorgeirsson and Óskar Guðlaugsson have established the beginnings of an online Old Norse course, with some samples of how Old Norse sounded.

Svá skyldi goð gjalda
gram reki bönd af löndum
reið sé rögn ok Óðinn
rán míns féar hánum
fólkmýgi lát flýja
Freyr ok Njörðr af jörðum
leiðisk lofða stríði
landáss þanns vé grandar.

(Click on the stanza above to download an MP3 with its pronunciation)>

Other online resources for Old Norse include this online version of Zoega's Dictionary of Old Norse by some highly industrious neo-pagans that I know, Rob's Old Norse Page for a beginner's perspective on the language and Peter Petersson's The Old Norse Language.

The most accessible books on Old Norse include Michael Barnes, A New Introduction to Old Norse - Grammar, which needs to be used with its Reader and Glossary companion volumes. The grandaddy of books in English on Old Norse is E.V. Gordon's An Introduction to Old Norse, which assumes its readers are as familiar with declensions and other grammtical accidence as Oxbridge scholars of the 1930s were and so could be hard work for beginners these days.

Once you've mastered all that you can read the sagas online at Netútgáfan or read them in manuscript form at Saganet

Cheers,
Thiu