I recently stumbled on another method of dealing with tantrums, which I am still waiting to try out on Liam in earnest.
It is probably an age old "remedy", yet not as commonly bandies about as the ignoring method - called Holding time.
When LO is in a terrific froth, bear hug him and force him to stay in your arms, basically pinning him to your body, he will go thru various degrees of anger, and tears and screaming and fighting, so it takes strength and perserverance.
But while doing this you need to gently and calming say things like "I know you are frustrated and mommy will help you cope with that once you have calmed down" or " your feelings are very strong right now, let mommy help you take control of them" etc.
I have spoken to someone who did this with her daughter and she says that her 11 year old daughter will still come to her and say "Mommy, something is not right, please hold me and help me thru it"
As I said, I still need to try it out, but now the little monkey has decided on other forms of manipulation to get his way - we have not had a serious tantrum for about 2 months