Reddit reviews Make: Getting Started with Processing

I haven't really used any tutorials to do Processing, however one book has helped me to get on my way: http://www.amazon.com/Getting-Started-Processing-Casey-Reas/dp/144937980X

Further, just try to decompose the image into simple to do instructions. First, learn how to draw a triangle. Second, find a way to draw a lot of these triangles packed together. Thirdly, make the triangles have a random color. Fourthly, generate the colors with different limits, like 'in this location of the image I only want these kind of colors or this color'. That's all there really is to these images, I guess. Good luck!

I just bought Getting Started With Processing for my son, and it looks like a great introduction to programming in general.

Processing uses a dialect of Java. You get immediate feedback in the programming environment and get to play around with graphics right away (which make it fun to learn). The book builds on little projects with chapters on variables, loops, arrays, classes, etc.

It reminds me of similar books I used to learn BASIC as a kid. It's not written with kids in mind, but rather for nonprogrammers. Still, it's very approachable.

Edit: Check out OpenProcessing for a collection of "sketches" (short processing programs) that people have posted. Source code is shown as well.