Comment 5 for bug 629244

http://askubuntu.com/questions/321532/how-to-make-ubuntu-13-04-work-with-displaylink-monitor

Try with a Kernel 3.9+
I followed this instructions and it works (do not use Nvidia native driver, use the opensource one).
It's slow but woks!
You can share windows (dragging them) between your different graphic cards!