I used to be able to trackstand for about 15 secs or so when I was a kid on my BMX bike. Haven't tried it more recently.

As for keeping a car in gear at a light, I found it a lot easier on my clutch-foot to keep the car in neutral and pay attention to the other lights. When the crosstraffic would get a yellow, I'd clutch and then slip it into first. This gave the same effect as being ready for the light without killing my left foot all the time. But as you said, different strokes...