well, i must admit to having used lots of techniques with honking or aggressive motorists...

when i was younger i would always react negatively, yelling, shooting the finger or whatever. i quite often would chase motorists and then have a huge screaming match. but although it feels good i don't really think it usually does much good. also as road rage and gun use has climbed iit's also not the safest thing to do. A few years back in downtown Portland of all places (the guy was a conservative from the country) i also got into a fist fight with a guy and i was assaulted in Houston in my car -- there was construction and we merged from 1 to 2 lanes and i had been sitting in traffic for over 50 minutes and some guy was driving his SUV over the construction barriers so i pulled over a little to block him. he honked and flashed lights and then the traffic ahead moved a little and with my window down at about 5mph a fist from out of nowhere connected with my jaw - i figured anone driving over barriers and assaulting someone wasn't particularly sane so i rolled the window up and pulled back over to let him by and ignored him as he yelled at me as he passed - i'm not a coward or anything but what's the use in this situation?

anyway, most of the time i use the smile and wave and thank you and i think it does usually work, although sometimes i'm too pissed off to think and still shoot the finger -- for example this morning i had to turn left and moved from the right to the left lane to make a left turn just as a light turned green and the driver did not have to slow down or anything but he hokned wildly his disapproval

what i have been doing recently that seems to have a little more effect and also feels good - when someone does something really dangerous, i chase them down and catch them at a light (usually possible) and then either rap on their window as velocipedio mentioned or in some cases i park myself and my bike in front of their car to get even more attention. Then i VERY NICELY and calmly explain something like "excuse me, what you did back there was really dangerous. i understand that you might be in a hurry or whatever and for you it might be a $200 fender-bender or mess up your paint job or ticket or insurance claim, but for me this was a serious threat to my life. could you please keep an eye out for cyclists in the future?"

sometimes people react rudely or defensively or state that i should be on the sidewalk or something, but quite often people appolgize - maybe many do it just b/c they're scared of me or something...

on the positive side, i fairly often have motorists who after having a close call (turning in front of me being the most common) will make an effort to verbally apologize and i am almost always friendly even if they endangered my life with their driving mistake or inattention... i figure they're be more careful next time if i'm nice