Known as Bear to Deadheads, Owsley Stanley was an incredibly important person in the development of the Grateful Dead and in the 1960s counter culture that changed the world. Owsley died recently in a car accident. I had no direct experience with him, and I've never done acid, of which Owsley was a prolific producer who took the art to its highest form.
Here are a couple of obituaries that provide background on an incredible life. The Oakland Tribune provides lots of history. The New York Times reminds of Owsley's influence on those who came along much later.
NY Times
Oakland Tribune