Get rid of grease stains on shirts - and yellow 'pits! Grease: 1 tsp. Dawn dishwashing detergent, 3-4 tablespoons of hydrogen peroxide, and a couple tablespoons of baking soda. Yellowing: one part Dawn dishwashing liquid mixed with two parts hydrogen peroxide and some baking soda.
Arm pit stains...I have actually tried this and it works great! I use about 2T of baking soda, 1t of Dawn, and about 2t hydrogen peroxide (for those who need exact measurements!). Make a paste then rub onto the stain. I let it dry overnight the first time, the second time just threw it in the washer, both came out clean. Used on shirts other than white to