April from Wildflowers and Whimsy shares a free pattern for her bustle back halter dress for little girls. This is such a pretty dress! It’s a fairly simple halter dress on the front, but the back opens into rows and rows of ruffles. Her pattern will make a size 3 dress. If you need a different size you could draft your own using her pattern as a shaping guide, and a garment that fits the child as a sizing guide. Get the pattern and tutorial.
[photo from Wildflowers and Whimsy]