Apple Developer Website & Apple Developer on iTunes is really a Gold Mine of Knowledge for Apple Mac OSX Developer, iOS Developer & Web Developer with WebKit.
Apple Developer Videos or WWDC Session Videos given on website or on iTunes (You have to sign in to website with Apple Developer ID which will redirect you to it’s iTunes Page) is really big opportunity for people who have interest & want to learn about this technologies.
Being myself graphic & web designer I found it pretty much helpful & informative.