Knol is a Google web service. My search under cancer produced the listing which further led me to the link to History of Cancer Treatment.
Another knol on Science 2.0: Web-Enabled Biomedical Knowledge Discovery"…discusses how web technologies can be used by researchers to share early stage biomedical discoveries. The goal is to speed up discoveries that could make a difference in the lives of millions of people" and another very interesting item on Cloud Computing.
Know is definitely an interesting tool and a resource to explore. One thought that comes to my mind is MERLOT integrating Google's knol as a feature.