For the preppy petite, here are a few pieces I saw on the Ralph Lauren site that may interest you:
Classic straight leg black jean
Aden Linen Twill Jacket
Vaughan Short Jacket
I'm not too sure about the skirts and dresses (especially the dress), as they all look like they could overwhelm a petite figure.
The site also doesn't list inseam lengths for the pants. Ralph Lauren Petites ranges from 2P to 14P, and they're more true-to-size (so you may have to take a size up). I have a jacket from them that is a 2P and I wear a 0P in jackets at Banana Republic and Ann Taylor.
COMPLETELY OFF TOPIC AND SHAMELESS PLUG: Don't forget to participate in this week's Prospere Magazine survey!
