This is a short one:

Just use this command to turn off your screen:

xset dpms force off

This won't only blank it, but really turn it off (no background lighting).
I like to keep the shortcut on the Desktop, so I can turn listen to podcasts without the screen lighting my room at night :P

And for a timed shutdown, I simply use this:

sleep 3600 && shutdown -h now

(this will wait for 3600 seconds (aka: 1 hour) and then shut the PC down)