Hi L.,
I nursed my son until he was almost three. Two books that helped me were "The no-cry sleep solution" by Elizabeth Pantley (I think). I can't remember now, but it may be geared more to younger babies. And "The Happiest Toddler on the Block" (can't remember the author).
One thing that helped me was counting. I would nurse for quite a long time. While nursing I would tell him that we were going to stop for a break soon. Then we would stop and of course he would want to start again. I told him we wouldn't start again until I counted to 100. I would count in a slow, monotonous voice and he would usually fall asleep (if not, I would nurse for a little more and then go through the routine again).
I know many woman have had success with letting their child hold or put a hand on their breast in stead of nursing. My son often (and still does occasionally) just wanted to hold my hand while lying beside him.
Also, my son invented the tummy cuddle for us during weaning. Instead of nursing, he would ask for a tummy cuddle. He would pull up his shirt and push mine up over my stomach and he would lie on top of me - tummy to tummy, skin to skin.
The Happiest Toddler on the Block had a technique that I used too. I remember my son was still in the crib when I tried this so he was younger (I seemed to fall in and out of nursing to sleep and then trying to break the habit and then starting again). I would nurse and then put him down, very cheerfully, and say good night and leave the room. When he cried for me I would go back in immediately, cheerfully, and sing a little song, nurse for less than a minute if had to, say night night again and leave the room. The key here is to remain calm and cheerful every time you do it. The book says that you may have to do this 20 times the first night (I think I had to do it about 8 or 10 times the first night, about 5 times the second night and only about 2 times the third night). You want to teach them that you are dependable, you hear them and will respond to them if they need you - but at the same time they are learning to fall asleep alone. My son was younger when I used this technique and I'm not sure if it will work with an older child.
But I think variations of this can work. Lying down with a child for a while and then saying "I'll be back in a few minutes. I have to go do the dishes," then coming back in a few minutes later helps your son practice being by himself and trying to sleep. I think it is important to keep your word if you tell him you are coming back so he learns to trust you and believe what you say. But you do not have to come back in for long before you leave again to "make a phone call" or something.
One last thing. We have some music that I would play for my son that he associates with sleep. Even now, if he is having a hard time falling asleep he will ask for the music.
Good luck with it. You will find a way that works for you!
-C.