I thought the answer about how Native Americans think children sleep better on the floor was VERY interesting. When we began transitioning my daughter out of our bed, that is exactly where she slept, on a folded up foam mattress-topper. Let me be a voice of reassurance and tell you that, no matter how stubborn your child is now and how hard it is, he CAN and WILL eventually sleep on his own. It's a matter of consistency on your part, which can be very, very hard when they wake up in the middle of the night and you're tired and you know darn well he'll fall asleep with you. I know, I've been there.
We transitioned our daughter (who's three now) very slowly, first leaving her in her bed for short amounts of time, and eventually expecting longer and longer bouts. She now sleeps in her bed until until the sun comes up, but she does still unfortunately wake up usually once a night (we're working on that). If you want this to happen more quickly, here is what I recommend: Tell your son that everyone sleeps better and is more happy if he sleeps in his own bed. For several nights, put him down in his bed, even if you have to stay next to him until he falls asleep at first. When he wakes up, put him back down in his bed. If he's anything like my daughter was, he'll fight you and you will have to be firm. (You know your son best. If his resistance is too strong to where you know he's extremely upset, don't push too hard. The key is to consistently TRY so he knows what you want from him, but he also knows that you're not just being mean.) See how this goes. If he needs a little extra incentive, make a poster with several squares, and give him a sticker in the morning each time he stays in bed until the designated time (the easiest time is when the sun comes up, since it's something he can see for himself. Or you can set an alarm and tell him he can come in your bed when the alarm goes off.)
We didn't do the sticker thing until we knew for sure that she was capable of putting herself back to sleep (this depends on being able to get themselves to sleep in the first place), but it did help a lot. This is just a quick synopsis. If you want more detail, I wrote all about it here: http://www.mothersclick.com/group/sleep-forum
You need to join the site but it's free just like Mamasource.
Anyway, good luck to you. Remember that it can happen, but that it will take consistency and patience on your part. Oh yeah, and someone else mentioned "The No-Cry Sleep Solution." I would recommend the Toddler and Preschool version of this book. It's geared for, well, toddlers and preschoolers.