I have a two yr old and we're expecting our next baby in March/April of '07. I am a childcare provider, so that right there helps, I have always been with other children and surrounded by children who need me, so I think that will help a bit, but I know he'll still have some feelings of 'resentment' or jealousy towards the baby when he reaslize he won't be going home at the end of the night. Lol. Things we're doing or planning on doing to help our son adjust to the change:
Children's books and video's geared towards accepting a new baby into the family. Arthur has a great video, my son loves it. There is a great book called 'God Gave Us You.' we bought this for our son last Christmas, it now has a sequel called 'God Gave Us Two.' Made specifically to help children learn about their new babies.
We refer to the baby in my tummy as 'Dylan's' baby, just so he understands that he'll be the big brother and get to help out.
Allowing a child to help out, not making him/her feel as though they have to walk on egg shells around the new baby is a definite must. This can cause resentment.
Having special time set aside just for the child that does not include the new baby, maybe having grandparents care for the baby and taking your son out to dinner at his favorite resteraunt with Mommy and Daddy, etc.
Last but definitely NOT least, patience and lots of it. With your child's need to adjust and transition into the new life style.
I wish you and your family the best! And congrats on your little addition!!!! Let us know how things turn out.