It's so hard! For me, knee-length is 39" or longer from shoulder to hem. Hemming a floor length dresses is always an option. I usually manage to find something beautiful, but still black and somber. Their usually the kind of dresses that would work at the office if I just put a cardigan over them. Here's a great example I've been considering for a semi-formal event coming up: http://www.trashydiva.com/site/indexSHOP.html
But why can't I ever get something in a color, lace, a print, or something