I've been meaning to post a link to this for some time -- MoreCloth.com is a very cool site with a color portal that allows you to find fabrics on Etsy or Glorious Fabrics. They also have an excellent blog on textile design and printing. The fabric selector works like this; you click somewhere on a color strip:
And it takes you to a selection of available fabrics in that color range:
Bottom: Joel Dewberry for Free Spirit
This is a fantastic tool; the blog is interesting and fun, and the color strips alone would be inspiring if they didn't awesomely find fabrics for you. I know it's sacrilegeous to say this, but I find Etsy to be not the most useful or compelling interface, so I appreciate this highly visual and colorful way of navigating its fabric options.