If they've got some lovely fabric or cutesey designs on them, you could disassemble the front piece from the back. Then you could use that front panel on a pillow, purse, quilt....some cheeky fun stuff for your girlfriends. Or you could sew up the edges and make little panty pillows.
If the fabric is lacey, you could use it to make some little sachets with some homemade potpourri inside.
You might be able to use the plain fabric pieces in a patchwork way.
With the stringy bits of the thongs, you could maybe somehow create hair bands, bracelets, etc. This is assuming that they may not be instantly recognized as underwear bits if they are separated from the structure of the undies.edited to add: looks like ishtar and I were on the same page with the patchwork as we typed our replies at the same time!