PBR MATERIALS BY 3D-WOLF (2.79+ principle node included).
TEXTURES.COM (old CGTextures) commercial and free textures.
BLENDER CLOUD. Tutorials, models,scenes, textures... subscription required.
References? Inspiration? Try PINTEREST
Commercial Archviz models, textures, materials... 3DSKY
ARCHIVE3D for free models
BLENDSWAP . A lot of free stuff for Blender here
FREE3D... yes, free 3D models
BIM FURNITURE FREE OBJECTS If you don't know how to use them, import them to Blender with this ADDON
A lot of Blender stuff for Archviz here, at BLENDER3DARCHITECT
Commercial models and materials for 3D: FLYINGARCHITECTURE
