The first one may be what you are looking for:  http://processing.org/learning/books/

OK, that's great that you want to know more!

The tutorials are nice:
http://www.processing.org/learning/
(There are also examples
http://www.processing.org/learning/basics
http://www.processing.org/learning/topics
More Examles you'll find in the IDE itself: Menu File|Examples...)

The reference is great and shows a lot of Code:
http://www.processing.org/reference/

On another platform you'll find collections for topics:
http://www.openprocessing.org/collections/

Or you learn by doing when you set yourself a medium goal for a program, start programming it and when you have questions, ask here.

Greetings, Chrisir  

Cool!
You both were a lot of help, Thanks :)

on the start site are more links a little further down...
http://www.processing.org