What Kinds of Grains are Gluten Free?

According to the Whole Grains Council, the following grains are gluten free:

Amaranth
Buckwheat
Corn
Millet
Montina
Quinoa
Rice
Sorghum
Teff
Wild Rice

The following grains contain gluten:

Wheat
Rye
Barley
Spelt
Triticale
Bulgur
Semolina
Oats* Note, oats are generally gluten free but can be processed with items containing wheat, causing cross contamination.