At a new M.'s group the facilitator told us about Fels Naptha soap. It is an old-fashioned laundry bar soap made by Dial. I have found it at the local grocery store, Wal-Mart, and Ace Hardware. Sometimes it is in the laundry aisle where it should be. Occasionally I have found it by the regular bar soap-although it is definitely not for washing hands or bathing. Fels Naptha gets out all the stains from my toddlers clothing & mine too. It even gets out the stains from clothes that I had washed & dried AND then realized there was a stain I forgot to pre-treat. My washing machine has the option of including an extra rinse cycle. Whenever I use a lot of the soap to remove stains I choose the extra rinse just to be sure there's no residue left on the clothing that could irriate my son's skin.
The other products I have have good luck with are Zout and Oxy Clean. In fact, I used to soak my son's super stained stuff in Oxy Clean when he was really small. Diaper leaks and lots of spitting up.
Good luck!