This is one I found and loved but can't use myself because I don't have a washer and dryer in my home! I just use my parents and didn't want to move this container around.
What you need:
-An airtight container
-2 sponges cut in half, total of 4 pieces
-1 cup liquid fabric softener
-2 cups water
Mix the water and fabric softener in the container and add the 4 small sponges letting the mixture soak into them. When you are ready to use fish one sponge out of the container, squeeze out the excess and toss it in the dryer with wet clothes. When finished put the used sponge back in the container for next time.