Here are some links to pages that are very informative and that I have found to be useful.
Linda is a canine nutritional consultant and writes articles about numberous different health issues in Great Danes.
Information on the dangers of unnecessary vaccinations. Suggested vaccination protocol is provided.
There is literally a ton of information about dogs and events on this site.
This is the official Great Dane parent club.
One of our local dog clubs. The offer different types of classes such as obedience and show etc.
Another local dog club.