A couple of people have asked me this in the comments. According to Joggles (where I buy it), "Soy Silk is made from the waste of the tofu manufacturing process - recycling at its best! This fabulous fiber is soft, lustrous, feels much like silk roving." You can find it here; it is really beautiful stuff (and feels like silk too).
Several of the other supplies in my postcards and atcs were purchased (or could be purchased) from Joggles too. Foils, Bonash powder, mulberry bark, silk throwsers waste, Pelmet Vilene, chiffon scarves, even the wool felt. Now I'm not affiliated with Joggles in any way, I'm just a very satisfied customer.
About the only things I use that can't be purchased from Joggles are my embellishing machine and my sewing machine!