This year I have decided to put some artistic flair into the garden and plant some plants that would actually dye clothing, yarn, and other fabrics. Plant dyes can either come from the roots, flowers, or foliage of various plants - this
website has a great list of which plants, which part of the plant and which mordant to use when processing the dye.
Here are my favorites that I will try to be growing in my raised garden bed this year, I'll post updates as the garden progresses:
Dyers Woad: (first year leaves only)
Before:

After:
Madder: (root)
Before:

After:
Tansy: (flower and stock - two different colors yellow vs. olive-green)
Before:

After: