Any suggestions on good Software for help in "sketching out" a cake design?

Free would be preferred

google sketchup is free.

there's a drawing module in google docs (free) that is similar to the drawing module in Word and MS Publisher.

I use MS Publisher for main drawing and then do touch ups in PhotoFiltre (free)

ARe you looking for something like this?

http://www.weddingcakedesignpro.com/