jailbreaking iOS 4.3 on Windows with Sn0wbreeze 2.3. It should work with the iPhone 4 and 3GS, iPad and iPod touch.
We don't have any personal experience with Sn0wbreeze here at Download Squad, but the process seems easy enough. Like the PwnageTool Mac jailbreak of iOS 4.3, this is a tethered jailbreak -- and remember, as there isn't a working unlock for iOS 4.3 yet, this jailbreak won't unlock your iPhone.
If you manage to successfully jailbreak your phone, let us know in the comments.