Crowdsourced Testing: A Quick Overview. I first heard of it (and the broader crowdsourcing topic) at the Jul 2008 TMF in a talk by James Whittaker (who said it was part of Microsoft’s vision of the future).
I’ve briefly looked at, but not used:
I’m aware of, but have not looked at:
I’m sure there are (and will be) others.
* I’ve since met the uTest team lead for my case study and would happily engage him in a full-time role.