Learning Pd

• The examples that come with Pd itself (under Help menu) are the first source. Starting with the simplest constructs and methodically introducing topics with very good explanations.
• ctrl-click on an object to open the associated helpfile which is a working illustrations with good explanations.
• ctrl-click on the canvas and you get a list of Pd objects arranged by topics (e.g. scroll down to see how you handle MIDI etc.)
• The Floss Manual for Pd starts with how to install and goes on to explain basic synthesis ideas with Pd.
• Johannes Kriedler's tutorials are an excellent source as is his book Loadbang.
• Andy Farnell's  book on sound design. 
• An excellent set of examples patches from Alexandre Torres Porres (which will eventually result in a book)
• This video tutorial is the first in a good series from Dr. Rafael Hernandez.

But the most important thing to remember: you have to actually do. Open patches, change parameters, add objects, change the sounds. Reading about or watching others create patches isn't enough.