Second that. I have a few old boxes lying around but nowhere near enough of the right pieces.. Also, I have heard there was actually a designer program which allowed you to do CAD style model and then gave you a part list to order... that may be quite useful too...
EDIT:
trying now:
http://ldd.lego.com/download/default.aspxLet us know if you get something reasonable out of the Lego Designer. I looked at it and didn't know where to start :-/