fabric dyeing is just about my favorite past time! :)
i usually use procion dyes from Dharma Trading company, but have had some fun and good outcomes from good old rit dye.
it is one of those activities that some people really jump into and love doing (like me) and then there are people who do not like the process at all and prefer to purchase their fabrics. if you want to just try it out Dharma sells some really good beginner kits...you can even get a batiking kit and learn to make batiks. it is a good way to try it out without a huge investment. one of our local quilt shops offer classes frequently dying fabrics, thats another way to try it out if you can find a class near you. there are so many different dyeing techniques, i never tire of dyeing my own fabrics! :)