Well, it sounds like you're having a test of wills, and your son is winning. So, take a deep breath and relax.
It is a very common issue (as you can tell from the responses), for children to whine more with mom than with dad. Let's face it, our husbands are good at turning a cold or indifferent shoulder to stuff they don't lke or feel they have to deal with. We mothers, born nurturers, have a much harder time doing that.
Although you didn't give any details about when and over what these tantrums happen, I have to different approaches. One in dealing with the tantrums and one which deals with preventing them.
I agree with the other women in that you need to establish your discipline consequences and stick to them consistently (with your husband's backing). Your son needs to learn that mom is not going to put up with this behavior, and the quickest way for him to learn is through appropriate consequences and your "indifference" to his reaction. In other words, let the consequences work their magic, because (let's face it) your angry response is helping his cause more than yours.
Although it is hard to learn to do, try to remove yourself from the situation so that you do not give in to your anger which your son is trying to ignite because he's mad. I usually try to find humor out of the fact that the temper tantrum (if not physical) is a silly act and there really isn't anything he can do about his situation, really. Do I manage to pull this off every time - no way, but I get better at it with each episode. My child is settling down more quickly and I am spending more time laughing (to myself) than frustrated.
The best behavior modeling trick is getting kids to think they are in control of their circumstances. "You can choose to act that way, but it will get you a time out, or you can choose to calm down and come play a game with mommy. I would rather you choose to come play with me, but if you want to spend time in time-out, then that's okay, too."
Also, let him know disappointment and anger are acceptable feelings, but throwing tantrums is not acceptable behavior. Give him ways to cool down, but let him use his toddler authority to decide how. If he can't make a good choice, then you "help" him by putting him in time out (if that is your method) since he can't think of a good way. Keep delivering the consequence until he "straightens up" for a minute or two, so you know he's settled. I would follow up with a reminder of his choice of bad behavior, praise him for calming down, give him a hug and send him on his way.
You may need to put other things on hold while you deal with taming these tantrums (because it will take several times for him to get the picture), but stick it out. The sooner you deal with bad behavior the "easier" it is to break.
If he does have a good day or deals well with a situation he might be tempted to throw a fit about, praise him for his good choices in being a good boy.
On the other approach: give some time to how you might be able to prevent these tantrums (like adjusting his sleep time). Some of them may be coming from situations that, if handled differently, would not produce a tantrum. He may be a child that needs to know some things up front like "we'll be leaving soon so I am giving you 5 more minutes because you've been so good", or "you can play with this toy, but in five minutes, we're going to do ..." or "mommy needs to do this, but when I am done we're going to that", etc. I think you get the picture. By prepping your son for what is about to happen or setting his expectations up front, you might be able to help him cope better with incident and eliminate the tantrums.
Good luck.