I've just finished reading a new ebook called "Square" by photographer Andrew S Gibson. I have always liked the square format, as many pictures suit this more than a rectangular shape. Most DSLR cameras have a square format. It's easy to keep in mind though when you're composing a shot, that you want it to finish up as a square, therefore you can crop your pics later in the editing process. I've put this collection together from existing pics in a 4:3 format then cropped them.