Is there any way to remove stains (e.g. from curries and pasta sauces) from plastic containers?
After washing them, fill them with a mild bleach solution (one tablespoon for each cup of water) and let them out in the sun exposing the stain for a whole day.  Make sure children and animals cannot reach the containers with bleach. 

There used to be a product called Cascade Plastic Booster that you could add to your dishwasher that would remove the stains.  It's no longer sold but its main ingredient was benzoyl peroxide at 5%, which you may buy in most drugstores.