http://www.cakecentral.com/modules.php?name=coppermine&file=displayimage&meta=search&type=full&cat=0&pos=1 here is a pic of one of the cakes in the galleries. You could probably use a sheet cake to make it and cut the shape you need out of that or maybe make a square and a round cut the round inhalf and use it for the ends. Just a thought. hope this helps. you can decorate it with the bday boys fav colors.
Go the galleries and under search put skateboard-there are 2 there! I did one but haven't uploaded the picture yet-I did a 9x13 and sort of trimmed one end-used cupcakes connected with a straw underneath for the wheels and set it on a brick underneath the board-couldn't see it but wanted the wheels to be there-had an old skateboarder topper to put on top-you could even do an edible image or BCT of some of the top skateboarders logos etc.
Here is one I did when I first started out, not that great, but the boy I did it for loved it. He wanted it black with his name in blue letters.
Lisa
I would have to crave one out~ perhaps with it on its side so that the wheels arent on top....but hey I love all the ones I have seen on here and the internet..... I am sure you will be great once you do it~!
This is a really cool skateboard cake! 
http://familyfun.go.com/recipes/special/cake/cake_skateboard/
~Denise
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