Cut up a bar of soap to use at the gym.
My family recently joined the ymca. The kids adore swimming but I hate sending an entire bar of soap with my 7 year old into the locker room. We were losing soap and I know he would drop it so that it would gather all the yucky floor germs. Now I just cut up a bar and add a little chunk to a zip lock, and go. When we get home I open the zip lock and let the soap dry for another use. These generally give us 2 or 3 trips to the gym. Each bar of soap can easily be cut up into 12 or so chuncks