J.C.
I don't have a boy, but in addition to all the great advice here, my daughter really liked the book "Everyone Poops". It was a gift, and boy am I glad. It shows how and where different animals and babies, children, and grownups poop by illustration.
I also got my little one excited bu letting her choose her own undies at Target. They have all kinds of great characters to choose from. I did have to put her potty in front of the TV to make it work, and let her run around w/ out any pull-ups on when we were at home in the mornings, because she would just go hide in the corner and poop in her pull-up when she thought I wasn't looking, and she wouldn't tell me when she had to go.
I hope this helps!