Is there a RentAPhD.com type service?
wheels: I suspect the results wouldn't be remarkably better than using normal freelancing sites and it'd be suspect to falsifying credentials.  Beyond that, a PhD does say something about a candidate, but presuming you'd want them for a development task, it doesn't speak much to their suitability for performing that task.One place that you might have luck would be on the ACM job boards.  Many of the SIG announcement lists primarily cover open positions.  While I'm often critical of the ACM, that would seem to have a similar target audience to what you're after.