I was watcing supernanny and this technique, although as it is described here, seems to be for a slightly older child, I saw her do it with a crib sleeping child. It stops the crying but takes commitment but it worked, and it is less tramatic for the child and you, hope this helps....
Sleep Seperation Technique
It seems harmless enough, lying down with your child while he goes to sleep, but it could be that sleeping by himself at night is one of his biggest steps towards independence.
Also, getting time to yourself in the evening means you’ll be on top form when it all starts again tomorrow! An unbroken night’s sleep is crucial to your child’s development and staying tucked up in bed all night could make a clingy child less dependent in the daytime, too.
Steps to get a good night’s sleep
Follow a calming bedtime routine.
Once you’ve put the little one to bed, don’t sit or lie down beside them. Sit on the floor instead, keeping your head down so they can see your profile but not your eyes, turn the light off and say “now it’s time to be quiet and go to sleep”.
If your child carries on chatting to you, insist that “it’s sleep time now” in a gentle but firm voice and don’t get drawn into a discussion.
If they get out of bed, put them back with a kiss and a cuddle the first time, just a kiss the second time, then with minimal physical contact after that. This part can be really hard, especially as the nights go on, but consistency and a kind tone will help your child feel secure in their bed without the anxiety of being left alone.
Little by little, move further away from the bed each night.
Eventually, you’ll be sitting with the door open, and finally you can say goodnight and go downstairs.
This technique will help your child get used to sleeping alone in a bed. It will also make it easier for you to gain a period of blissful independence each evening before you, too, head for dreamland.