Hi David, there isn't currently any actual transparency.

But there are a couple of alternatives currently - one is to hide faces of the exterior parts only like Burr mentions (The scene browser in v2 has a control under Types > Faces which can be useful for this). That can give you a display as seen in this gallery item:
http://moi3d.com/gallery/viewitem.php?id=239&subid=1

Also there is a hidden-line display where hidden edges are drawn with a faint dashed line style. That can give some visual information similar to transparency. To enable that go to Options > View > Display hidden lines, and also in v2 there is a checkbox for it on the Side pane under the View palette.

If you need a more detailed presentation with more effects, then usually the method people use for that is to export the model to a rendering program where there is a lot of control over different materials and visual properties.

- Michael