New obsession: blouse-to-two part dresses! Thanks, Anthropologie!
Here's one of the dresses I made and a few pics, based on Anthro's Bustling Avenues Dress:

This started as a nice quality cotton gauzy, shapeless J.Jill blouse that I got at the Goodwill Outlet for $1.39/lb. So, like 25 cents.
There are darts, but it's still loose and shapeless. It had 3/4 length sleeves, an open neck, and some cross-stitch details at the ends of the (wimpy) darts.
I used a yard of cute black and white cotton and this darling vintage pattern. I didn't have enough fabric to do the buttons.
(View C, the yellow one, without the buttons).
I cut off the sleeves of the blouse, into a flattering tank top style. I cut off the bottom of it to a little longer than natural waist, and gathered, and attached to a black cotton waistband I added:
I had to take in the side seams, too. Then I added the faux yoke at the front in the neckline (all made from the bottom 5" of the shirt, which I had cut off) and made a little rosette from the sleeve scraps!!