Here are some of the places I found in Japan as well as links to other people's blogs, websites and information. Please feel free to let me know of other places to find fabric or craft materials in Tokyo.
adjacent to the national important cultural property "Nitenmon Gate"
The gallery has a permanent exhibition of Boro.
Special exhibition on working women's clothes till April 2011.
Amuse Gallery is very close to Sensoji temple in Asakusa. Go right down the shopping street, Nakamise Dori then at the main shrine turn right into a side road. Amuse Gallery is on your left opposite a Duty free camera shop.
Instructions and map on the website.
Shinjuku Station South Exit. Turn right, walk about 5 minutes, museum is on the other side of the road.
A road of textile shops.
Check out Floating World blog for instructions on how to get there.
This is a craft/hobby/textile shop.
Shops in Kamata, Kichijoji, Yokohama and more, click on link to see a list.
Go to Kichijoji Station, exit via Park Exit, walk out the station exit and straight ahead. Yuzawaya is on the 7th and 8th floor of Marui Kichijoji store (head for the store with the big OIOI on it). It is no longer in the station building (which I found out by wandering around for ages). Click on this link to see a picture of the logo.
Mega DIY/craft shop with shops in Shinjuku, Shibuya, Ikebukuro etc. Branches in cities across Japan.
Has a good range of English books, craft books in Japanese and English as well as calenders and magazines. The best one I found was in Shinjuku but there are other stores in cities across Japan.