How to recruit participants for online experiments? We are currently doing a study where we thought it might be smart to try out the possibilities of recruiting participants from the Internet. I was thinking it might be best to ask more experienced members, where would be the best kinds of places to publicize the experiment, and what strategies they would recommend to this?
One approach that has become popular amongst many social and cognitive scientists is the use of Amazon Mechanical Turk, which is an internet piecework marketplace.  Many people have used this for recruiting study participants, and IRBs have been quite receptive to its use.

Designing studies for Mechanical Turk is challenging, and presents different issues than designing for in-person studies.  A number of online resources exist that discuss the advantages and challenges (e.g., this blog, this paper, and this website).  Mechanical Turk also poses sampling issues---as has been noted, however, typical recruitment methods also end up getting almost exclusively WIERD participants, so it's unclear how much of an issue that actually is.