PLoS is a great resource. My favorite example for the value of free content research is actually an example of a PLOS/Wikipedia synergy:
http://en.wikipedia.org/wiki/Gorilla#Natural_tool_use_by_all_the_.22great_ap...
The photos demonstrating natural tool use by a female gorilla come from a PLoS Biology journal. Such use of photos by researchers in Wikipedia is of course only possible because of the free license. The synergies will only increase as we and others create new projects like Wikiversity where they can emerge.
Erik