That's what I would do- melt them all down and start from scratch again. There are other, more creative things that could be done, like shaving the soaps and creating new bars with the shavings (poured over by clear soap with a new fragrance) but since you have a large box of leftovers, that would be a tedious task.
Susan

another option is mark them down. I used to mark last years leftovers down to a dollar & have a sale box on the table.....never lasted for the whole show.
And they would also buy some new soap too.....

Hazel