Disney, from ~Ruffles and Stuff~ has an easy tutorial on how to create sassy toddler bubble skirts from a pair of old tights and a little fabric.
Look at these she created:
Full tutorial with step-by-step photo instructions found here: http://www.rufflesandstuff.com/2009/12/bubble-skirt-from-tights-scraps.htm
*Tip: After you ruffle the material, use a zig-zag stitch to attach the fabric to the tights. The zig-zag allows the tights to stretch a bit without breaking the threads. If you do hear from breaking, it's from the original gathering stitch which is just fine since it should be secure with the zig-zag. You can always pullout the gathering stitched before the toddler wears it as well. Either way works.