I've been using google sketchup today. It's the first time i've used it and it's actually pretty cool. It's very user friendly, but i am still quite bad at it. I think i'll probably be using it to build my sets in and then use these virtual sets to help me frame my film, etc. I've also been thinking about using the models i build in it to paint over in photoshop or flash to use as backgrounds. I did a quick test of this today.
1) Here's a model of a table i made, plain.
2) Here's the same model but with a marble effect applied from google sketchup.
3) Here, i exported the model from Sketchup as a JPEG, opened it in Photoshop and had a quick crack at painting over it just to see how it would look.