Milk Thistle is likely the best herb for detoxifying the liver.  It also helps to protect and strengthen this vital organ as it contains Silymarin which regenerates liver cells and guards the organ from damage by pollutants, toxins, and viral invaders.  It is a powerful antioxidant.  Health benefits of include: 
Stimulates liver function and rebuilds liver cells that have been damaged by illness, improper diet, or excessive alcohol intake.  For overall liver health, especially useful for those with liver cancer, cirrhosis, and hepatitis.  
Clears up acne.
May help lower bad cholesterol and increase good cholesterol. 
Helps soothe symptoms of irritable bowel syndrome and Chrohn's disease.
May help treat and prevent gallstones, and aids kidney function.
Aids digestion, and as an inflammatory, it also helps with inflamed intestines.
Has been used as an emergency antidote for mushroom poisoning, particularly with the Death Cap variety.
Studies in test tubes have shown that this herb helps cancer cells from reproducing, shortens their life span, and reduces blood supply to tumors.