XRandR is used to configure which display ports are enabled (e.g. LCD, VGA and DVI), and to configure display modes and properties such as orientation, reflection and DPI.

zarfy
LxRandr
Grandr
Configure Additional Display
Video Index

http://www.thinkwiki.org/wiki/Xorg_RandR_1.2
http://www.xfree86.org/current/xrandr.1.html
http://wiki.debian.org/XStrikeForce/HowToRandR12
Scaling with Panning bug
Enhanced Zoom Desktop