Accidents happen. Your child leaves a crayon in a pocket and you fail to find it before throwing the clothes into the washing machine. If you have a load of laundry riddled with crayon streaks, don't despair. Rewash the load using the hottest water the fabric will allow, and add 1/2 to 1 full small box baking soda to the load. You can also pretreat a crayon mark by sprinkling baking soda onto a damp cloth and then rubbing it into the fabric. Afterward, just launder as usual.
But we can't always blame laundry accidents on kids -- sometimes it's our own doing. If you've managed to mix some colored clothes in with a load of whites, don't fret! You may not have done permanent damage. Before putting anything in the dryer, soak the damp clothes in a solution of baking soda and warm water to which you've added 1/2 cup salt and 1/2 cup detergent. Choose an earth-friendly detergent if you like, then wash as usual.