We have an old cotton slipcover waiting to be dyed, but just thinking of finding a space and a tub that's large enough for the fabric to not be bunched up, moving hot water across the floor, having to stir it all without splashing any on the floor or turning the cat orange... it's enough to keep it on our "to-do someday" list. But we just heard about iDye, a fabric dye made to be tossed into the washing machine, and it seems worth trying out...
The typical grocery store dyes (Rit, etc) are powders that you open, mix with boiling water and gingerly stir. Its almost guaranteed that you'll get get something accidentally stained in the process when you use them, and it's very hard to dye large pieces evenly because the fabric bunches. One of the great things about iDye is that its a sealed dye packet that dissolves in water. You just toss the dye in the washing machine, run it for 30 minutes adding salt or vinegar (depending on your fabric), wash it out and that's it. So you don't have to get pans, clothes you are wearing, spoons or even the bathtub stained with dye. And there's no cleanup. We assume you could even use this in a laudromat without endangering the person who uses the machine after you, but would love to hear from readers who have used it to reassure us on this.
iDye comes in 38 colors — including 8 colors for polyesters and nylons (although it looks like you need to use the stovetop method for these fabrics). There's even a Color Remover which you can use to lighten or remove the color from fabric without using bleach. We'll post our results here after we use it, and have gotten some awesome tips on dying fabrics from helpful AT readers in this post.
>>> Jacquard's website
>>> Available locally in Boston at Artists Supply in Central Square
>>> Available online here (with nice photos of the colors)