While there is no actual API for the LED flash on Windows Phone 7.5 handsets, developer davepermen has found a way to still bring an LED flash light for those whoâ€™s OEMS did not see fit to provide one.
As he revealed in our comments here, developers can access the camera, and the flashlight is on as long as the camera focuses. The trick is to put "Focus()" into an endless loop, to never stop focussing, and thus never stop glowing the led.
The fruits of his efforts is White Light, a free app which will only work for those with Mango handsets. If the LED does not work the app still provide a dazzling white screen if all else fails.
White Light can be found in Marketplace here.