Here is a list of other useful resources:

Manhattan Dyeing Service, Ltd. is a sample fabric dyeing facility located just minutes from midtown Manhattan. Over the past decade, they have accumulated a formidable list of clients inclusive of over 500 major apparel manufacturers, such as Victoria's Secret.
True Color Fabric Dyeing. Your clothing and other textiles can be dyed to a professional, commercial quality to look fresh and new. Rejuvenate faded, dull or stained fabrics to original shade or darker. Custom color requests are always welcome.
Paula Burch's All About Hand Dyeing. Instructions and examples for all sorts of dyeing: tie dyeing, batik, hand painting, low water immersion.
Dharma Trading's is a great resource for fabrics and dyes.
Lots of information on fabrics is available through fabrics.net
The Craft Studio may also be worth a visit.
Aurora Silk offers custom dyework on your own fabric or textile items.
The Silk Connection offers textiles, silks, cottons, rayons and linens.
More about the wonderful world of colors can be found at Pantone.