Fabrics
Linen
Fabrics - Store.com - Decent linen at a good price. Sales available.
Fashion Fabrics Club
96 District Fabrics - Awesome linen at a decent price. Also have hemp and fustian.
Wool
Woolrich Fabrics - Great selection but not the lowest prices; if you need a specific color they likely have it.
BBlack and Sons - Good coat weight wool.
Hamilton Dry Goods - Email first, they don't update their site often.
Candle Llight Valley Fabrics - Decent stock and some good sales
Fashion Fabrics Club - Often has good light weight wools in stock
Denver Fabrics - Now part of Fashion Fabrics Club
Fabric.com - Hit or miss on their stock.
Carolina Calicoes - They have more than is on their website. Email them for what they have is stock. Warning they travel allot and are slow to email back sometimes.
Hemp
Hemp Traders
Silk
Rupert, Gibbon & Spider, Inc.
Thai Silks
Dharma Trading Co.
Dyes
Dharma Trading Co.
Linen and Real Gold Threads
Hedgehog Handworks
Threadneedle Street