iOS 5 beta 3 is jailbreakable by RedSn0w 0.9.8 b1. DevTeam hacker MuscleNerd has confirmed that the RedSn0w 0.9.8 b1 jailbreak works
Today’s 5.0b3 can be jailbroken with last month’s redsn0w http://is.gd/6eek4Y (point it at 5.0b1 IPSW..devs only please!)
RedSn0w 0.9.8 b1 jailbreak works on all devices, exect iPad 2. This means you can get a tethered jailbreak on Windows and Mac OS for iPhone 3GS,
You can download RedSn0w 0.9.8 b1 for Windows and Mac OS here.