Grammars:

E. V. Gordon: An Introduction to Old Norse
http://www.amazon.com/Introduction-Old-Norse-E-Gordon/dp/0198111843/ref=sr_1_1/105-8577773-7362853?ie=UTF8&s=books&qid=1189597652&sr=1-1

Michael Barnes: A New Introduction to Old Norse
http://www.amazon.com/New-Introduction-Norse-Michael-Barnes/dp/0903521652/ref=sr_1_1/105-8577773-7362853?ie=UTF8&s=books&qid=1189597856&sr=1-1

Or you can order the latter title directly, along with the volumes 2
and 3 (the reader and glossary).
US: http://asu.edu/clas/acmrs/publications/mrts/vsnr.html
UK: http://www.viking-society.group.shef.ac.uk/publications.htm


Some online resources:

Old Norse Online (Todd B. Krause and Jonathan Slocum; 10 lessons +
grammar + runes).
http://www.utexas.edu/cola/depts/lrc/eieol/norol-TC-X.html

Old Icelandic Course Materials (Tarrin Wills: referrence grammar +
texts: Iðunn and Skaði, Þrymskviða + vocabulary)
http://teaching.arts.usyd.edu.au/english/2000/icel/

Henry Sweet "Icelandic Primer" (specifically Old Icelandic/Norse,
rather than the modern language) http://www.gutenberg.org/etext/5424

Cours d'Islandais Ancien (French introduction to Old Icelandic, with
grammar & parallel Norse/French texts) http://anamnese.online.fr/islensk/

Materialien und Erläuterungen zur Grammatik des Altisländischen
(Einführung in die altisländische Sprache, Hartmut Röhn)
http://www2.rz.hu-berlin.de/bragi/b4/b4fornislenskukver_de_hr.pdf