[jharding]

This doesn't really answer your question, but you should take a look at 99designs. Depending on your needs, it could help make finding and working with designers pretty painless. I used it because I needed a logo for a side project and I had a great experience.

[sontek]

I love 99designs for logos but we are building a web application, so a lot of interface design, and I haven't seen many success stories for that type of thing out of crowd sourced design sites.