I have been closely following the trend to show the bra through the blouse. I have seen people doing it in several different ways.

Wear a see through top or dress or shirt

I have seen Katie Holmes, Amy Smart, Hilary Duff, Leele Sobieski, and Heather Graham.

Bra is not fully covered by the dress

Rachel Stevens, Britney Spears, Brooke Hogan, and Susan Atwell.

Bra peeking at the top of the dress

Miranda Kerr, Nadia Bjorlin, Mena Suvari, and Miley Cyrus.

Now we have Zoe Saldana and Chloe Sevigny doing exactly that by wearing dresses that are totally open in the front to flash their bras.