I used to do this to my girls' jeans after school let out. Great way to boost the summer wardrobe for next to nothing! Transform an old pair of jeans into adorable summer shorts using bias tape. Instructions on the site.
to aprons This is another interesting and funny way how to use old jeans. Take one trouser leg and cut it in apron shape. Take some other old fabric, and cut it in thin ribbon. Sew them together to get aprons from the old jeans as shown bellow.