I've only been commuting a few months so the only recent incident I can recall is when I was too busy fiddling with my watch at the lights and completely missed them turning green. Obviously the reaction to that particular hoot was an apologetic wave.
I have found, though, that I'm FAR more chilled on the bike than I was in the car. I don't know if it's because I'm more visible, more audible or just too knackered to care, but I find myself letting the most stupid acts of idiocy go. In my car I'd be hooting and swearing like a mad thing!
True what an earlier poster said about use of cycle lanes, though. I freely admit that until I started commuting by bike myself I couldn't understand for the life of me why cyclists didn't use (what seemed to be) a perfectly good cycle lane close to my house. As it was a multi-lane road, cyclists in the inside lane seemed a crazy and highly annoying proposition. I never beeped or yelled at them but as a driver it used to rightly p*** me off.
That was until I started using said cycle path myself! Only then did I appreciate just how useless off-road cycle paths truly are, despite the pretty green tarmac and nice pictures of bikes all over them. A few weeks and a couple of cars-turning-left-right-in-front-of-me close shaves later and I'm using the road with the rest of them!