How about a braided bath mat
Cut off the waistbands, then cut off the crotches, so you're left with a "tube" of fabric.
cut the remaining fabric in 2" strips (now you have a giant "o" of fabric pieces)
cut 1 end of each piece, now you have a strip of fabric- sew each strip together end-to-end.
at your local craft shop you can find a pack of 3 little metal v-shaped fabric turning clips
(google the words "braiding fabric tools") how these little clips work is that you slide your
strips of fabric into them and they "roll the edges inward, and tucks them inside to prevent
fraying and it looks neater.
So you take 3 long strips of your fabric panties, feed the fabric strips into the fabric clips,
pin the 3 starting ends together with a safety pin - maybe anchor it to a pillow to hold it
or pin to your couch to hold it still. start the braiding! you're going to end up with a big
braided "snake" keep attaching more panty strips to the end if you want it longer. when
you're done decide what shape you want your bath mat (oval is easy). start hand-sewing
from the back side going around and around to hold it all together.
this bath mat will feel like you're stepping out of a spa -it'll be very soft, water absorbant,
and easy to wash! - I wanna make one out of panties now
I've made one from a thin terrycloth which I recycled from a bathrobe lining-
good luck and have fun