I found Nap Time Crafting through UCreate. She has a great tutorial for "pillowcase dresses (pc.d.)."
I made a pc.d. few weeks ago for my daughter from the instructions that I found on a room somewhere, with a few alterations of my own. For example, instead of placing the ribbon on the side to tie I put it in the back. I did use a regular pillowcase, but I found that it was too wide for Rory's frame.
I can't wait to try the refined instructions.