Hi C.,
I know exactly what you are going through. My son is 4 and for the past 8-12 months has been sleeping in between my husband and I. We have tried many tactics to get him to sleep in his own room. We put in a tv and dvd player, hoping he would fall asleep watching tv (this worked with our 2 girls), He has a nite light, His entire room is Ohio State themed, since he loves the team, we hoped this would make it more appealing. One of my friends said she had to turn the door knob around and lock her kids in, just to get them to sleep in their own beds. I tried this too, but he started kicking and banging on the door, and I just couldn't take it and neither could my two girls, who had to get up for school in the morning. At this point I think I am going to have to get the advice of my Pediatrician, because I am at a loss. I hope some of the ideas that I have tried will work for you. Like I said the TV worked for both of my girls around the age of 2-4 and they always fell asleep. I personally think they just liked having some noise in the room :)
Hope you find an answer!
N.