Drachenkosmos This site has a lot to offer. However, the "dragon" issue is less dealt with from the POV of literature, but more from a scintific POV. BTW, you can also find an old article about "The Dragon in the Works of J.R.R. Tolkien," which I once wrote.
The site is in German only.
The Dragon Valley You can admire very nice dragon images here. And more things are offered. The site is primarily in German