Thanks to a tip from Kathryn's comment below I have found some possibilities at J. Cr*ew. And more encouragingly I looked at other places I love but never thought of. There are three dresses on their way from Ann Taylor. Well technically four but that one is for someone else's wedding. They were all on sale and came with free shipping.
Let this be a lesson to all you lurkers. Speak up! You never know when you'll give me a breakthrough.
http://www.fillorburst.com/mt-tb.cgi/1135
I bought my dress for my sister in law's wedding this August at JCrew, from their formal-ish collection. It's really, really cute.
I bought the sophia long silk dress in navy and wore it to a wedding a year ago that Scott was the bestman. I must have gotten 10 great comments on it. I loved it and Jcrew for making it! So, I highly recommend their dresses.