You'll find more textures and accessories for the original DAZ dragon than any others, and bloodsong's Dragon Factory CD is great if you want to build it yourself, but here are some alternatives:

Anton's Storybook Dragon : DAZ
Anton's Dragon Skeleton : DAZ
Mock's Dragon : Renderosity Marketplace
PhilC's Dragon : Renderosity Marketplace
blbarrett's Sea Dragon : Renderosity Marketplace
konan's Ultimate Dragon : Innuendo Software
PhilC's original dragon freebie : Fantasy 3D