I don't know why this is question is asked so much, really.

Ask yourself this, "Where do you go about finding programmers?"

A good answer for this is usually at local meet up groups. Programmers don't have a monopoly on such things.

Some ideas for local meet ups:

http://refreshingcities.org

Full disclosure: I'm a co-founder of Refresh Portland (http://refreshportland.org)

http://www.ixda.org/ http://www.sigchi.org/ http://webdesign.meetup.com/

For example, we recently had Jared Spool speak for free at Oregon's chapter of SIGCHI, CHIFOO. It was free and jam packed with around 180+ designers.

I'm sure that there are a quite a few groups where designers go to gather and talk about topics that are important to them.

So, my advice is to go to a designer meet up and mingle. Even if you don't find a designer right away, just tell them about your project and they might know a friend of a friend.