I am fascinated by natural dyeing, though I am forced to admit that this is the only lot I have actually done! It is my homespun, dyed with lemon-scented gum. I used alum as the mordant, it being the only one I had to hand (it's used in swimming pools). Actually getting other mordants has put me off a bit - they would all have to be got mailorder or by trecking across town. Yes, they are poisonous too, but then I keep poisonous dyes in the shed too so the mordants could be stored there.
I am now keen on trying it out with fabrics. I have been reading about rust dyeing, and one of my tutors last semester had done a lot of cloth dyeing with dirt. I met a textile artist last weekend who had been using local plants to great effect, too.