My son will be three in June.No matter where we go or who we are with he seem to think everything belongs to him or is "mine: and won't let anyone else play with or on what he is currntly playing with or on.For instance.If we're at the park and he's on the slide he will stand at the stairs of the slide and block t he other children from even getting on the slide.ect..ect..ect... This drives me crazy.What can I do ?

Well I hate to tell you but your son is a very normal 2yo. Sharing takes time and doesn't come easy. But don't worry it will improve. Just tell him we are nice to our friends, and it nice to share with others and then they will share with you etc.

On the rare occasion he does share, give him lots and I means lots of positive praise. Tell him how wonderful that was. Best wishes