Alex goes through stages of bedtime fears. I think it's a form of separation anxiety. She'll be fine for a while and then go through a period of being afraid. When we ask what she's afraid of, she'll say, "My room," or "the dark," or "my closet." The other night she told me, "I keep hearing ominous sounds in my room." :-) I didn't even know she knew that word!
We have developed a system that works for us. We put a sleeping bag or blanket on the floor of our bedroom. We tell her that whenever she is afraid, she is welcome to come in and sleep on the floor as long as she is quiet. When kindergarten started, she did start coming in about every other night. Gradually she's coming in less and less. It helps that our floor is not quite as comfortable as her bed.
I had forgotten all about the sleep fairy until she reminded me a few days ago. When she was 3, we had a really hard time getting her to go to sleep and stay in her room. We told her that the sleep fairy would leave her a prize under her pillow if she went to bed quietly and stayed quiet all night. The sleep fairy left pennies, raisins, pieces of candy, stickers, and occasionally small toys.
The other day she said she wanted the sleep fairy to come again. Maybe this was her way of telling me she is ready to plan on sleeping in her room every night again. So the sleep fairy has been visiting. Now that Sam is a little older, of course he wants in on the action, so he gets a prize too. I have to admit it's a lot of fun being the sleep fairy and coming up with new things to put under their pillows. I love to watch them sleep.