BedTime Woes!!! HELP!

Does anyone else DREAD getting their 19 month old to bed? I used to rock him to sleep in my arms every night untill about 18 months when he just refused...kicked...screamed...slapped me, while trying to get him down, so I took this as a cue maybe he is ready to go to sleep by himself in his crib. So, (his pedia. actually recommended letting him go to sleep by himself) I started putting him in his crib around the same time every night (about 8:45) and the first few nights he did wonderful, never cried, just feel asleep. After that first week though, he will scream bloody murder for about 20 mins before eventually falling asleep. He still does, every night, it's heartbraking. So, I tried going back to rocking him and he refuses that too. I don't know what to do. I feel horrible about just letting him cry but nothing else works!!!! What adds to the distress is the fact that we live with my parents and my grandmother and when I was a baby it was unheard of to let a baby "cry it out". They will come to me and say "how can you just let him cry like that", "don't you hear him", or "go get him and rock him"...etc! Things like that don't help me out at all! Do you all have any ideas on how I can help him fall asleep and what should I say to his grandparents?