The Great Dane Homepage.  A site which offers information on many topics related to the breed.  A useful site for new owners.
http://www.ualberta.ca/~dc8/dane.htm

The Great Dane Club of America.  A useful site for prospective buyers and new owners.
http://www.gdca.org./

The Great Dane health foundation.  A popular site to obtain answers to many health related questions.
http://www.gdhfa.org/

The Danesonline site.  A popular site for the new and experienced Great Dane owners.
http://www.danesonline.com/

The Great Dane Reporter website has been the leading magazine for Great Danes for more than 25 years. As always, the printed magazine is a great research tool.  It contains educational articles on health, temperament, breeding, obedience, rescue, judging and much more.
http://www.gdr.com/

Ever thought of crate training?  Here is some information that may help answer questions, and decide on what is best for you.
http://www.pethelp.net/crates.html

Great Dane books for new or experienced owners
http://www.dogbiz.com/dogs-grp3/great-dane/great-dane-books.htm