Breadboard is a software platform for developing and conducting human interaction experiments on networks. It allows researchers to rapidly design experiments using a flexible domain-specific language and provides researchers with immediate access to a diverse pool of online participants. It was developed by the Yale Institute for Network Science -- Human Nature Lab.
The software is open source but using it requires some effort in learning the "groovy" language for defining experiments and in connecting to Amazon Mechanical Turk. The Demography Lab maintains a virtual machine farm and a small but growing community of users who can help you put your experiment on line. Contact Dennis Feehan (email@example.com) if you are interested in exploring the possibilities.