Where is the Best Place to Post a RFP?

I have a friend who showed me a mockup for a large-ish project. It's
too big for me and he also wants an iPad/iPhone app to go along with
it. I think Drupal would be a good tool for the website but I'm
wondering where people think is best to post the RFP?

I would think here and maybe on d.o. I suppose the weeding out of the
good vs bad proposals can't be made easier by posting here or there or
elsewhere, but I thought I would ask first before I advise him. :)

Thanks,
Fred