The approach we took was to start as early as possible.
the day after our son was born, we sent my sister-in-law home with one of the swaddling cloths we had used. She put the cloth on our bed, so that our cats could get used to the smell (the cats normally sleep on the bed).
When we brought him home, we kept him apart from the cats for the first week or so, and then started letting the cats in to see him while he was sleeping. Since our cats are generally pretty affectionate, they wanted to be where we were, which made it easier to get them used to being around my son (at least while he was asleep or feeding).
A quiet creature that isn't moving very much is much easier for a cat to adjust to than a screaming toddler that is constantly moving and trying to grab tails, so start early! :P
It is important that the cats always feel like they have a way out if they start to feel uncomfortable. Don't pick them up and hold them near the baby. Don't block the way to the exit.
Within a month, one of our cats took to napping in his crib with him. Our oldest started avoiding him when he started running around the house, but now, 3 years later, lets him pet her. Our most skittish cat, who is only rarely seen by visitors, is comfortable enough with my son to not run away when he walks by, but this is a fairly recent change.
It did help quite a bit that as soon as my son was old enough, we assigned him the task of feeding the cats (we'd fill their bowls in the morning with a small amount of canned food mixed with dry, and he'd hand them out to each cat).