You can melt them and make one large bar out of them. (Or two or three, depending on the number of small bars that you have collected.)
Unwrap all of your small bars of soap and toss into a small saucepan. Add some water and turn heat to medium. (I’m sure you could do this in a microwave also.)
Place the lid over it and check back every now and then to stir. Watch carefully so the water doesn’t cook dry. You may need to add more but don’t overdo the water because the soap will become slimy and won’t harden back up again the way it should. Once the bars have melted enough to stir together, stir vigorously until the soap is whipped up and soft enough to pour into a mold. Some soaps melt better than others so don’t despair if some don’t melt completely.
At this stage you may roll the soap into balls or other shapes, or spoon the mixture into a mold of some sort. I like to use a plastic travel soap container. It’s the perfect size for a large bar of soap and also flexible when turning the hardened bar back out of it.
When the soap has cooled and hardened turn it out of the mold and you have a nice big bar of soap instead of several worthless slivers.
When I’ve had more small bars to melt than would fit into one travel soap container I turned the melted soap into a cake pan then cut the cooled chunk of soap into nice sized bars.