You sound like you are frustrated with your son's behavior, and it is good that you are reaching out for help.  There are several things that you may want to think about when he has a temper tantrum.  The first and most critical thing is what happens after his inappropriate behavior?  does he get his way?  If so, you are reinforcing the behavior that you want him to stop!  It will be very important that you not give in or let him get what he wants when he acts this way.   You have to be firm and not give in to his tantrums or they will continue.  
 
Is it just naps that you are having a problem with?  Some kids have a tough time settling down for a nap.  Do you have a regular routine prior to getting him to lay down?  Let him know a few minutes ahead of time that it will be time to lay down--you could even set a timer. Also, do you do anything to quiet him down like read a book when he lays down?    These things may better help him transition from play time to nap time.    
 
You may also want to consider giving him a small treat or using a sticker chart to reinforce him when he does a good job of laying down to take a nap.  You can't really do it at naptime, but if your child misbehaves, a quick 1-2 minute time out can quickly send a message that what he has done is wrong.  Make sure it is in a spot where he cannot do anything but sit, and where you can monitor his behavior.  
 
Hopefully these ideas will help you to feel that you are setting your child on the right track and that you feel more positive about his behavior.
 
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Dear Angel, I know how rough this can be! One personal piece of advice I can give is to make sure to make sure to stay calm know matter how frustrated you get. Remember that through all this, your son is learning how to manage his anger by observing the adults in his life (and he is watching very carefully!) I have used personal calming techniques like counting backwards from ten, breathing deeply, or just expressing verbally how I feel in a calm voice. For some professional advice and some psychological background on tantrums, check out the  article below for strategies to use when he throws a fit.

I understand your frustration.  Children, especially babies act out as their way of communication.  Since they don't have the words, they sometimes scream, hit, or kick to show their annoyance.  There are several methods you can try to help this problem.  Maybe changing the nap time?  Or have you thought about playing with him for half an hour until he tires out and sleeps on his own?  In addition, you may have mommy and me time where he quietly plays with his toys in his crib or stares at his toes, instead of a full nap.  
I hope some of these suggestions help.
 
The following is a reference article dealing with how to get through a tantrum.
 
http://www.education.com/reference/article/Ref_Getting_Through/
 
Good Luck,
Rachna

Here is another great article on "12 Ways to Deal with Temper Tantrums" by child psychologist Dr. Lisa Medoff. Hope this helps you!