(1) The Middle Finger: Short, concise, and straight to the point. There's not really a whole lot of room for debate when executing this strategy.
(2) Laying Down Your Horn: Is sure to piss them off, which I suppose is the point of expressing one's displeasure, but it does have the potential of pissing off other drivers as well. However, if you find that perfect balance between letting everyone know what a jackass the other guy is, without coming off as a jackass yourself, well then Bravo to you, and give yourself a pat on the back.
(3) Yelling, Screaming, Cursing: Good way to vent your emotions, but this can often end very badly, so I wouldn't necessarily recommend it.
(4) Just fucking ramming into that son of a bitch: They cut you off, they pissed you off, just fucking hit 'em, that'll teach them a lesson.
(5) The thumbs up: I actually somewhat inadvertently used this technique today, while encountering an Asian woman who was beyond driving ra tarded. I don't know, I just couldn't bring myself to give a lady the finger, and this form of sarcasm at her piss poor driving skills actually made me feel better, so maybe I'll use it more often.