Here's a dump truck cake I made for my great-nephew a few months back. Its' out of the Wilton fondant book, only I changed the colors up a little. I tried to show each step with pictures. It was fairly easy to do - just took a little more time than most of the other cakes I've made. And this one was completely edible - no crafting foam!
One change I will make when I do it again: the wheels look like they belong on a motor cycle instead of a truck! I should have made the tires wider with smaller hubs.