LINK: RasPi B.skp
Threw this SketchUp file together as part of my latest hardware project. There are some additional construction lines left in for convenience for those wishing to align components to the connectors and mounting holes on the RasPi board.
I made every effort to ensure that the model is dimensionally as accurately proportioned as possible. If in doubt check against your own RasPi to confirm.
Enjoy.