Running Xorg on a netbook with a 1024x600 resolution can cause some annoyances when trying to give a presentation and hooking up to an external display that has a different aspect ratio. By default on Arch linux, Xorg seems to map the resolution to the VGA1 output and scale the resolution to fit on the netbook's LVDS1 output, and then when you disconnect VGA1, the resolution doesn't switch back to your previous mode. Granted, I'm using icewm and gnome/kde might have spiffy scripts that take care of this for you already.
To fix this, I added the xrandr setups to my ~/Makefile:
presentation_undo: xrandr --output VGA1 --off xrandr --fb 1024x600 --output LVDS1 --mode 1024x600 --panning 0x0 presentation: xrandr --output VGA1 --mode 1024x768 --output LVDS1 --mode 1024x600 --panning 0x768 urxvt -fn "xft:Andale Mono:pixelsize=25"
which lets me run 'make presentation' in my homedir and get a working screen setup and an xterm that most people can read.