These are links I enjoy:
Doll Divas- This is what got me started on dioramas. The people who post are fabulous and the photographs of the dolls are great. One of the advantages is that, although they mostly feature Fashion Royalty and Barbie, I have also seen 16 inch dolls, smaller Japanese style dolls like Momoko, some BJDs, some Kish dolls, etc. It is a family friendly site and a great place to meet doll people and get questions answered. Don't miss their Diorama Divas section, which has lots of pictures and tips for dioramists.
Stinker's Stuff- Johanna has stories, amazing tutorials and even clothes for sale. (Warning there is some PG-13 material on this site.)
Plaza Mildendo- pricey, but fantastic furniture. Check out their fireplaces!!
Oakridge Hobbies- doors, windows and stair rails in 1:6 scale.
Miniatures.com- has many of the same things as Oakridge Hobbies, but cheaper. (Be sure to check measurements on all these.)