Looking for indigo day to day has brought me to researching the properties of indigo and artists who use indigo in their artwork:
Ann Hamilton discusses the inspirations behind her performance / installation indigo blue.
Natural Indigo Dye Fermentation Process
I made my own indigo bath the other day and it went very well. At first I was worried that I would some how mess it up by letting too much oxygen in but it turned out well. I dipped my yarn in four times and the color was a deep dark blue, I also dyed a second set of yarn, I dipped it 2 times and the color was a medium blue instead.