This hint allows you to sleep the display via AppleScript and the Active Screen Corners feature of Exposé. It is based on the script in this blog entry, which allows you to move the mouse cursor to the top left corner of the screen.
First of all, you need to set the Exposé functionality (in the Active Screen Corners section) of the top left corner to Sleep Display. Having done that, the following AppleScript will sleep the display:
(*
Source for the shell script:
http://hubionmac.com/wordpress/2009/09/maus-zeiger-in-applescript-via-python-bewegen/
*)
do shell script "python -c \"import objc;bndl = objc.loadBundle('CoreGraphics', globals(), '/System/Library/Frameworks/ApplicationServices.framework');objc.loadBundleFunctions(bndl, globals(),[('CGWarpMouseCursorPosition', 'v{CGPoint=ff}')]);CGWarpMouseCursorPosition((0, 0));\""
tell application "Finder" to activateMac OS X Hints
http://hints.macworld.com/article.php?story=20100418152304108