oh wait, i got my advice around the wrong way.
blackhole shaders are for when you want to render things that appear behind other things...
i meant to say, you could add everything to a render layer, and override the render stats 'visible'
hammer: was that question directed at me? i haven't rendered in layers for 2009 yet, but in 2008 the shadow was just black, even in the alpha channel...
that's a "Ch" pronounced as a "K"
Computer skills I should have:
Objective C, C#, Java, MEL. Python, C++, XML, JavaScript, XSLT, HTML, SQL, CSS, FXScript, Clips, SOAR, ActionScript, OpenGL, DirectX
Maya, XSI, Photoshop, AfterEffects, Motion, Illustrator, Flash, Swift3D