Sadly not, it's always been something I wanted to try. Theres plenty of resources on the net about diy moulding of various plastics.
I wouldn't recommend polystyrene on it's own though, you may want to 'alloy' it with ABS plastic for extra strength.

ABS plastic http://blog.makezine.com/archive/200...s_plastic.html

Unfortunately I have no idea how workable this goop is.