I have REALLY appreciated this thread. My almost 6 year old son is very much like many of these kids, and I have a lot of new ideas to try! Because I am naturally a positive person, the negativity has been particularly difficult for me to be patient with. What frustrates me the most is the unending hissy fits over tiny things like adjusting his chair, the wedgie he can never get rid of when he's angry (LOL), etc.
The main thing that has worked for us is having him run some laps around the house, which leads me to believe that finding ways to increase serotonin when we are heading towards an explosion will be helpful. I also need to learn to make taking some time alone be less like a punishment and more like helping him to cope with the bad feelings.
Anyway, thanks again everyone!