Learning things has always been possible through two main routes (many other are possible though, surely): learning through a reference and learning by example. Personally it’s quite hard for me to learn through reference – it’s like learning grammar and syntax of a foreigh language without speaking the language. There always must be examples of use. Many of them. But who made examples? Others. So, learning from others in an open (free software) world is crucial element of today’s information society IMHO. In the old days I learned HTML from other webpages.
Here are two sites packed with different processing examples to learn from: