Resources I have found useful (in no particular order):

• http://www.arrl.org
• http://www.radioelectronicschool.net
• http://en.wikipedia.org
• http://www.amateur-radio-wiki.net

• Amateur Radio Study Course -- Graeme Scott VK2KE
• Amateur Radio Study Guide -- Graeme Scott VK2KE
• The Novice Operators Theory Handbook -- Graeme Scott VK2KE

And the very best resource has been visiting my local radio club, Waverly Amateur Radio Society and talking with the hams there on our regular meeting days.