They are also really cute for framing transparencies that you've printed on. Inkjet printing would need to be embossed or it won't dry, but laser printing dries just fine.
You can layer the framed transparency over some patterned paper or other background, too.
Another idea is to make mini shaker boxes out of them. Use a transparency or scrap of a page protector for the top, run foam tape around the sides and fill them up with shakers - little beads, punchies, confetti, tiny shells, seeds - whatever fits your theme!