I'm working with some folks who get really irritated at having extra blank spaces at the end of the line. To make them happy, I went looking for how to highlight whitespace in Emacs. The default is way too much highlighting for me.
Here is the stripped down set of values for just highlighting trailing whitespace and turning that mode on for all files.
; Highlight trailing whitespace. (require 'whitespace) (setq whitespace-style (quote (face trailing newline))) (global-whitespace-mode 1)
This page also had hints on changing the highlight style.