Hi Wiggy. 
I used to have to always feed dd to sleep. She never took a dummy.
I used to lie with her in bed until she was asleep, unlatch, then creep away (if unlatching her hadn't woken her!)
Then I started unlatching her just before she was asleep, but staying very close, often with my arm across her legs, to stop her kicking.
After a few weeks of doing this I moved onto unlatching her and backing off a few inches and just lying next to her, no contact. I didn't say anything, kept my eyes closed, occasionally sneaking a glimpse to see if she'd dozed off. (Obviously if she became distressed I wouldn't just continue to ignor her)
I believe that was the stage where she finally learnt to put herself to sleep. The holy grail of self soothing!
Just recently, at around 6 months, she started to become more mobile so I knew I had to get her to fall asleep in her cot, not on our bed. It also meant that while I was lying beside her she was trying to reach for me and roll towards me. One day I got so frustrated with this that I just scooped her up, plonked her in her cot and left the room (to cry and eat chocolate)
Miraculously she fell asleep, all by herself, within minutes! 
I hope I'm not tempting fate by saying this but I've been able to 'plonk and leave' her about 8 times out of 10, over the last two weeks.
So, it's not 100% failsafe but we're getting there. At least I hope....
I can honestly say that I NEVER thought it would ever be possible. DD has been a nightmare to get to sleep since day 2.
Also, although I am not one for CC, we do leave her for a few minutes if she's grizzling, or doing her 'protesting cry', (often this happens immediately after I leave the room but only lasts a couple of minutes). We do go into her if it doesn't stop after about five minutes, or if it escalates to full blown howling. I think she just sometimes likes to let off steam.
Anyway, hope some of that may be useful.