Warnings
Mention should be made of the toxicity levels in some of the mordants used in home dyeing. Older books and magazines make no reference to this issue.
Chrome and tin are quite toxic, and should never be used in a house with insufficient ventilation, or by someone who is unaware of the dangers. Chrome has been proven to be a health risk if absorbed through the skin or inhaled (see links below). Iron and copper are less so, but can still be a health hazard with sufficient exposure. Disposing of these chemicals can be an issue, as they build up over time if just dumped into the backyard.
Also, some of the dyes and plants listed can be harmful to your health if not handled carefully. Always research your ingredients thoroughly before using (Lilly of the valley, madder, rhubarb leaves, etc).
Glass jars with tight-fitting lids are best for mordants, and to maintain potency and chemical stability keep away from direct sunlight and heat. If there are handling and safety instructions (Material Safety Data Sheets) it is best to keep it handy to the container (if not attached directly to it). Always keep mordants and dye materials out of the reach of children and pets.
Related How-Tos
Sources and Citations
[1]Article which explains a bit about chrome mordant and possible toxicity
[2]Potassium dichromate
[3]Hexavalent chromium