one of my friends just got one the j crew dresses for her boyfriend's friend's wedding. it's really cute. she got it in black for an evening wedding.
http://www.jcrew.com/catalog/product...atId=cat100143
A lot of their other dresses are cute too.
Every once in awhile I've found cute cocktail dresses at Macy's (they often have good sales, as well). I also like bloomies for dresses. (This is in addition to nordstrom of course, although I've found that nordstrom doesn't always have the best dress selection in their stores).