Most people find out about Permaculture through friends or the media (TV/Internet). For instance, Gardening Australia (ABC TV) often highlights permaculture demonstration sites. Since the 1990's, more and more excellent material is available on the Internet.
You can find out more about permaculture through:
Introduction to Permaculture courses [search the Net for your closest]
Permaculture Design Course (PDC)
Permaculture One (1978) Mollison & Holmgren. Despite its age, this is still a
great place to start. 127 pp.
Introduction to Permaculture (1991) Mollison & Mia Slay. 198 pp.
Permaculture Designers Manual (1988) Mollison. 576 pages; a huge text - not an easy starting point, but Billís concept was a single book to cover all PDC content.
The Permaculture Home Garden (1996) Linda Woodrow. More suited to tropical than temperate climates but very easy to read. 181 pp.
http://www.permaculturemelbourne.org.au [Permaculture Melbourne]
http://www.tagari.com [Bill Mollisonís website]
http://www.holmgren.com.au [David Holmgrenís website]
http://www.permacultureinternational.org [Australian site - good national info]
http://www.permaculturesa.org.au [Permaculture South Australia]
http://www.permaculture.co.uk [UK permaculture]
http://www.permacultureactivist.net [USA Permaculture]