This little application allows you to set the brightness level. The program is completely customizable (graphics and settings).

myLight is designed to run on HTC (tested on Diamond, Touch Pro and HD) in both portrait and landscape.

Changes:

Compatibility Bug
FingerMenu/HTC Menu Support
Turn Screen Off
Light Sensor Support
Enable/Disable LightSensor

http://forum.xda-developers.com/showthread.php?t=485141