Procion MX Dyes. They are fiber reactive dyes that will work on all natural fibers.
Fiber-arts.com carries both Jacquard's and Pro-chemical's MX dyes. I prefer Pro-chem's only b/c they have the most colors(never used them all but...) Both are quality brands. Dharma Trading uses the Jacquard dyes wh/ they have expanded on by making auxilary colors out of the basic colors.
Here is a chart that gives a basic run-down comparison between the pure and mixed MX dyes between the 3 dyehouses.