Other websites to check out:
Recreating Viking Clothing, Hilde Thunem – wonderful overviews of archeological evidence of trousers, serk (dress) and smokkr (apron-dress)
Viking Answer Lady, Christie Ward – a wealth of information on many aspects of Norse life by Mistress Gunnvör silfrahárr
Viking Resource for the Re-enactor, Carolyn Priest-Dorman – articles on clothing, textiles, etc by Mistress Þóra Sharptooth
Where I buy fabric:
I buy most of my linen from Fabrics-store.com. I use their 3.5 ounce natural or bleached white linen for my dresses, and their 5.3 oz linen for tunics, pants, and smokkr
For wool, I am very fond of Naturtuche – they are a German company with beautiful light weight wools in Viking-Age appropriate weaves. Shipping from Germany does take a little time, but I have had great luck with their customer services.
I also like Woven by Elsbeth for hand woven twill fabric and leg wraps. She is one of the few US source I have found for diamond twill fabric.