The Socially Mediated Internet Survey (SMIS) method is a cost-effective technique used to obtain web-based, adult samples for experimental research in political science. SMIS engages central figures in online social networks to help recruit participants among visitors to these websites, yielding sizable samples for experimental research. We present data from six samples collected using the SMIS method and compare them to those gathered by other sampling approaches such as Amazon's Mechanical Turk. While not representative of the general adult population, our SMIS samples are significantly more diverse than undergraduate convenience samples, not only demographically but also politically. We discuss the applicability of the method to experimental research and its usefulness for obtaining samples of special, politically relevant subpopulations such as political sophisticates and activists. We argue that the diversity of SMIS samples, along with the ability to capture highly engaged citizens, can circumvent questions about the artificiality of political behavior experiments entirely based on student samples and help to document sources of heterogeneous experimental treatment effects.