Participatory, Voluntary, random selection, kinda?

Inspired by SDMB Funniest Poster - A Contest

Suppose, we among the SDMB online community, want to make a random selection for something like the contest above. My suggestion in that thread was choose a subject matter for a witing contest, rather than no rules on subject matter at all.

I suggested we do that by pooling the URLs of wide variety online magazines and journals. I wanted to suggest we pick one randomly, but there my thinking broke down. I ended up suggesting that Hamlet simply choose one from the pool, because I couldn’t think of a way for the community as a whole to either make or validate the legimacy of a random selection. And I have no hesitation trusting Hamlet too make a fine selection, should Hamlet end up even making such a choice.

But supposing, later, for a more important/controversial/interesting contest, we, as an online community, want to witness/document/validate a random selection from a pool of choices generated non-randomly by Members.

How would we do it?