Currently using Freya on a T60 and wanted to turn off the screen on demand.
Using elementary's Hot Corners function, it's possible to set up a corner of your screen to respond to the mouse pointer this way, going blank, while the computer remains on (not suspend mode).
To do this, go to System Settings > Desktop > Hot Corners as below:
On the corner of your choice, click on the drop-down menu and select "Execute Custom Command" and copy the code below on the field "Custom Command", as shown above.
xset dpms force off
After this, whenever your mouse pointer hits the chosen corner, the screen will go blank until some activity occurs (mouse or keyboard activity).
Credit goes to neonsignal from http://www.linuxquestions.org/questions/linux-software-2/a-command-to-make-the-screen-go-blank-839037/