If they're worn and won't stay tied properly, just replace the laces. In fact, buy two pair when you go to the store and make a note of the length you bought.
Creative re-uses:
. Tie up plants in the garden;
. Bundle branches or newspaper for trash/recycling;
. Wash/bleach, then use as gift wrap ribbon;
. Tie around boxes to keep them closed while in storage;
. Macrame a plant holder - string beads along the length to make it even more interesting;
. Wash/bleach, then use as a border for a scrapbook or a photo frame;
. Donate to a marching band camp - they use them to carry their "Dot Books."