There was a proposal to overhaul wikipedia's front-page design, and wikimedia's corporate design, by holding a contest: http://en.wikipedia.org/wiki/Wikipedia:Design_overhaul%2C_2006
But designers are mostly opposed to contests, and pro designers don't usually compete in them (contests also pose problems for organizations on the recieving end) -- see Talk, http://en.wikipedia.org/wiki/Wikipedia_talk:Design_overhaul%2C_2006
So it looks like we have an offer from a visible designer to help us find pro-bono firms and designers who'd be willing to do the site for free (just not on spec). We should put out a call for portfolios.
Cheers (and sorry about the telegraphic style; I'm a bit tired)
Ben Yates