Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
.exe is a Windows Executable. Links for nightly builds for each platform are here: http://nightly.webkit.org/
Just download and launch. Why exactly do you want to use Webkit instead of Safari 5.1? Is there a certain feature/bug fix you want to try?
:apple:
 
I want to develop WebKit based applications and on Windows WebKit.exe show me an error message:

The procedure entry point u_strToUpper_4_0 could not be located in the dynamic link library icuuc40.dll.

On OS X I can open WebKit, but Safari (and my app) still runs with its original WebKit engine.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.