Just about to go to bed, sorry I didn't read a lot of other posts but this is what we did:

DS: waited until he was 1 year old. Prior to that we were giving him a cup of milk (went from bf to cup at 10mths, his choice) and holding him until he went to sleep.
Chose a long weekend or when DH didn't have to go to work for a week and let him cry for 10 mins before we went in, but I remember lying there listening to him cry for what seemed a long time the first night. Took a few hours the first night for him to learn we weren't going to pick him up.
2nd night we did the same as the first night (very hard not to give in but this is the key for the shortest period of pain) and he went to sleep within 2 hours, for the whole night.
3rd night went to sleep within 45 minutes.

DD: still bf but at 14 months I was so tired from working pt and bf and getting up to bf at night 2-3 times so again planned for DH to do the going in, so she knew she wouldn't get a feed.
Took 3 nights again, but not so much crying because she quickly got the message that only water was coming. So since October long weekend last year she stopped waking at night.
She kept bf in the morning until slowly weaned her off at 18 months.

I would suggest looking at Pinky McKay's website to see if you can find some tips there, as she supports gentle parenting and has some hints for getting them to sleep. She advocates choices that a respectful for parents and babies, so it is about what you think is the right thing for your baby and your family.

The guilt was there at the time for me, but I knew ultimately that the night bf especially had to stop as I just couldn't cope and it was affecting the kids, my work and me! So I put it into perspective that a few days in the scheme of things was not too bad. Having a very very supportive DH made it much easier because we were in it together so the timing was crucial not to affect his work etc.

Goodluck!