Front
I downloaded the reference card for version 8, the free one.
Camera>Standard Views>Front starts you out on a 2D plane. If you rotate, you can go to front view again and it snaps back. But your left with the 3D axes.
With PS Elements you can change line color, weight, and thickness. Is that even possible in Sketchup? I looked at something about "edge styles" but it looks more complicated than it's worth.
If I could use color lines, I'd be tempted to try a 3D wiring diagram. How cool would that be.... :)