This black and white one is from Target, and the dress I wore to my sister-in-laws wedding. It's very flattering because it has a tie at the waist and the fabric flows beautifully.
This navy one is from Loft. I bought it in green, and it also comes in light blue and yellow. It has a stretchy neckline so it easily pulls down. Loft also sells a shirt with the same basic style.
As I find more great dresses, I'll keep you posted!