iPhone dev-team has just released Redsn0w 0.9.8b4 to jailbreak iOS 5 beta 4. As most of you know that jailbroken device can't use OTA (Over-the-Air) update, but you can download the complete version of iOS 5 beta 4 directly form Apple's developer center.

Supported Devices:
iPhone 4
iPhone 3GS
iPod Touch 4G
iPod Touch 3G
iPad 1

Download Redsn0w 0.9.8b4 (Win)
Download Redsn0w 0.9.8b4 (Mac)