I.,
Just went through this with our son who turned three back in July. What worked for us was similar to to what worked for Deille. Now, I am a mom that rarely gives candy to my son. When he gets candy it is a big deal. Usually a few M&M's (like less than 5) is a big treat. Each time he would go pee pee he would get either 2 M&Ms or 2 gummy bears. He wouldn't go poopy in the potty though, he'd hide somewhere and go in his pants. When he would go poopy in the potty without any accident in his pants I gave him a lollipop. Then I'd call Daddy at work or Grandma/Grandpa to tell them all about it and they'd make a big deal out of it. We've even praised him for his accomplishments in front of our other parent friends and various other receptive/friendly people at church/grocery/etc. People were always very cooperative with this and got a kick out of it themselves.
After the second lollipop there have been no more accidents. He's been doing this consistently for about a month. We still give lollipops and make a big deal out of each poopy. I've read where it takes doing something 27 times to make a habit out of it. Just consistently keep up with something that your son really values as a reward and he'll have it in no time.
Also, if you're comfortable with it, we'd let our son see myself and my husband do our business in the potty which helped him see that it is something that "big people" do, and normal to do in the potty and not in his pants. Good luck!
One more thing, we went cold-turkey on the diapers and just do "pull-ups" for bed (we'll tackle bedtime in a few months). He wasn't really too happy to get poopy on his "Lightening" or "Thomas" underpants. We also made up a silly walk that would happen if a poopy got in your pants. He thought mommy looked pretty funny and didn't want that to happen to him.