I should have written this up ages ago, but I keep forgetting.
One of the first official "hacks" I performed as a parent involved the cheap little plastic washtub we got from the hospital - you know, the one they use to give the baby a bath at the hospital, and they can't sterilize them, so you get to take it home with you. Since we already had an official baby bathtub we'd gotten as a shower gift, we ended up turning the hospital tub into a stain removal center.
We kept the tub on the floor in our laundry room, and whenever one of Liza's pieces of clothes got stained, we'd throw it in the tub instead of the regular laundry. When the tub was full, I'd use a stain stick on all the stains, throw a scoop of OxyClean Baby into the tub, and fill it up with the hottest water I could get. I'd throw the clothes in and go so something else for an hour. When I was ready to start the clothes in the main washer, I'd pour the entire contents of the tub - clothes, water, and all - into the washer, along with the unstained clothes and detergent. And darned if 90% of the stains didn't come out!
This method had two benefits over some of my other options, which included soaking the clothes in a sink or in the washer itself. First of all, who wants to soak poop-stained clothes in a sink you're going to use for other stuff? Our laundry was in our bathroom, so I would have had to soak poopy pants in the sink where I wash my face and brush my teeth. Ick. And soaking clothes in the washer would have tied up the washer for an hour and used a lot more water.
Now that Liza's older and we don't have quite so many stains, the tub has been pressed into duty for a few other things, including puke bucket and place to put the kid when she's pooped in the tub. Not bad for an ugly plastic washtub we got for free!