Pretty much every part of the dandelion can be used, the only danger being that, if you are using dandelions from your yard, you need to pay attention to the types of fertilizers and insect killing chemicals you may have used on your yard. My mom used to use the leaves for tea, and to mix them in with salads sometimes. I have heard of using the roots for coffee, but haven't tried it. My wife brought it up just the other day, so she came across it somewhere too. Interesting, when I was looking through the plant catalog, I found that you can buy dandelion seeds, and after all these years of thinking of it as a weed. Another quite edible plant that often grows as a weed in the lawn is plantain; its broad-based leaves can be used in salads or soups. In an attempt to bring this thread back on-topic, it might be interesting to try some mixtures of coffee with dandelion roots. During times of shortages, I know that chicory was used as a coffee substitute and I used to be able to find Louisiana coffee that include chicory, and I thought that was good.