multiple monitors configuration without proprietary driver

[Luis Alberto]

Thank you everybody for helping me. I finally could drag the GNOME panels, as 
Christian recommended. The only thing I didn't get was putting the login 
screen on the correct monitor, but I guess that's a minor problem (I tried 
setting up two screens as David and Alex recommended, but then I was only able 
to get clones, so I'll will just leave it this way)

Again, thank you very much everybody.

Luis Ablerto