I know a lot of people were wondering what dress Krisen was wearing at Much, and after some research. I found what may actually be the dress.
It looks it looks to be the French Connection "Fast Jack" Plaid Dress.
It's not too expensive at $168.00, but for people on a budget like myself, Forever 21 sells a similar style dress for only $20.00.
EDIT: The Polka Dot Dress she wore to SPOILERS will be availiable Spring 2009 from DKNY! I don't know how much it will cost though.