I think all in all, this is a phase and with wise discipline much of it can be controlled so that you stay sane. I am just now seeing the light at the end of the tunnel - my son is 28 months old now and I recall that his behavior peaked around 23 months. It is better, especially now that he is saying more words and can express a little what he is feeling. I have learned from experience and advice from other moms that traditional time outs do not work for some 2 year olds. I think they don't get the concept - they jsut think you are walking away from them. I have used what I call the "together time out" where I will do time out with him, sitting next to him while he lays on the bed or in my arms crying, but I don't pay attention to him and I make no eye contact. After he calms, I look in his eyes and say, "I know, you are angry (or sad)! See angry?" and sometimes if I have one nearby I hold a mirror to show him his face. I figure that the more he can associate feelings and facial expressions with words, he can use the word next time. Also I find that looking in the mirror sort of "breaks" the tantrum a little. I find that timing out together works a lot more than walking away completely, and it has reduced the screaming. Now, even though he does not say the word, he will nod yes or no when I ask him if he is angry.
Then, I will say, "you want hug, feel all better?" after the time out is done (2 minutes) AND after he is calm (which can take longer than 2 minutes) - often he will say yes and the drama is over, at least for the moment. For now, I don't focus too much on trying to get him to understand the rules, just the cause and effect part of it (hit = time out, no mention of why hitting is bad, that it hurts, etc.) to keep it all very simple and not overwhelm him. My method does not work all the time - however, it works MOST of the time, and that is OK by me, considering that he is only 2 after all, and life can sometimes really be overwhelming for the little guy and he really cannot help himself.
Finally, I forgot to mention teething - this actually happen to me a few weeks back, when there was a sudden flare in his tantrums out of nowhere, and later I happened to notice his gum was swollen on one side. I tried a dose of Motrin and gave him cold fluids and it helped.