Dandelion is a very helpful plant. Not only is it easily found, but the whole plant is edible!
It is an aperient, a cholagogue, a diuretic, a stomachic and a tonic. It promotes the production of bile and removes excess water from the body resulting from liver problems.
The fresh juice is the most effective, but tea is also a very good way of consuming dandelion for it's medicinal properties. An infusion of the roots has reportedly been helpful when dealing with gallstones, jaundice, and some liver problems. The leaves can be tossed in a salad, and the flowers dried for infusion.

Edit: Source - Lust, John. The Herb Book. 1974. Bantham Books. p 170.