Theory's "Analba-Crunch" Dress (pictured right): simple linen dress that will go well with a cardigan or a jacket. Made from linen with a touch of rayon. Available in the pictured "barley" and black. $275; find it here.
Helen Berman's Floral Sheath Dress (pictured left): whether or not this dress is appropriate depends on your office. Even if paired with a black cardigan, the flowers simply may be too big and the colors to bright and the background too white for some offices. But it really is gorgeous. Made from cotton and nylon. $238; available here.
Calvin Klein's Cargo Shirtdress (pictured right): though this dress has slightly large cargo pockets in the front, I think the buttons and decorative tie at the waist combined with the button-front collared bodice makes this dress work-appropriate. Made from polyester and spandex; available only in the pictured khaki and black combination. $118; find it here.