Open terminal & type: “xrandr -s 1024×768”

Just replace 1024×768 with the resolution that you want and as long as it’s supported the display will switch immediately. Personally I came across wanting to do this to add it to the remote control button script in the previous post as Hulu Desktop uses alot of CPU at 1360×768 (Native resolution for my LG 37LG30 HDTV) and my video was dropping fames on my Linux Desktop (AMD 2Ghz Socket 939 single core). Here’s what I did to the script for reference:

begin
prog = irexec
remote = mceusb
button = RecTV
config = killall Boxee; xrandr -s 800×600 && huludesktop&
end
begin
prog = irexec
remote = mceusb
button = DVD
config = killall huludesktop; xrandr -s 1360×768 && /opt/boxee/run-boxee-desktop&
end
Note the && between changing the resolution and launching the new app, this ensures that the resolution change command has completed before the new app has been started.