There are great ideas as well as how to do shirring from a segment on Martha Stewart's tv show.
There are also tutorials on these terrific blogs found here and here.
For my dress, I cut 2 pieces 19" wide and 21" long. Caitlin's chest measurement is 18" in diameter, and since the fabric will shrink by half, plus there are 1/2" side seams, I'm figuring this will fit her perfectly. (I hope.)
I used some ribbon for the shoulder ties. I also found a little blue butterfly to stitch on the front.
Click on the image to make it larger to see the little butterfly.
The problem I encountered was that elastic in the bobbin would not stitch flat. So I used a special bobbin case that accepts thicker thread. It took me better part of the day to get it adjusted properly.
It's supposed to look like this.
So while this was an easy project, it was time consuming in terms of getting the bobbin tension correct. Actually, frustrating might be a better description.