iPhone Dev Team have just released redsnow 0.9.8b1 for Windows OS which will jailbreak iOS 5 Beta firmware on iPhone, iPod Touch and iPad. iOS 5 Beta jailbreak was released just a couple of days ago but for Mac users only. This redsnow jailbreak is in tethered mode only for now. As posted by the iPhone Dev Team, the Windows version of redsnow, just like the Mac version will overwrite unlockable basebands, which can be a problem if your phone is unlocked.

redsnow 0.9.8b1 supports :

* iPod touch 3G
* iPod touch 4G
* iPad 1
* iPhone3GS
* iPhone4 (GSM)
* iPhone4 (CDMA)

Download : redsnow 0.9.8b1 For Windows
Download : iOS 5 without a developer account
Tutorial : Jailbreak iOS 5 Using redsnow 0.9.8b1 [How To] 

Warning : Unlockers and those preserving thier unlockable basebands should STAY AWAY from this jailbreak. You will very likely lose your unlockable baseband if you try to install iOS 5.

The way redsnow works, you will very likely be able to use this on upcoming iOS5 betas, just by continuing to point redsnow at the iOS 5 IPSW.  So keep that IPSW file handy.