Permaculture is a sustainable form of agriculture that focuses on creating permanent systems, which mimic natural ecosystems. These cultivated ecosystems are designed to provide food, water, shelter and other materials necessary to create a closed system which is not dependent on outside inputs. The theory is based on the idea that a forest does not need fertilizer or outside inputs in order to flourish. While conventional permaculture does employ the use of animals, there are a growing number of individuals who are adapting this method in ways that do not involve animals.
North Carolina State University allows lectures to viewed for free from their permaculture course taught by Dr. Will Hooker. Dr. Hooker is extremely knowledgeable in this field and he also welcomes additional experts as guest speakers throughout the course. This is an excellent place to learn the fundamentals of permaculture.
You can find the lectures on the NC State website here.
*Update 3/8/2013 These lectures are also available for free download from itunes.