Phone Dev Team has released a new beta of redsn0w 0.9.5 for new iPhone OS 4 beta 4.

They have designed it to ease the jailbreaking of os 4.0

Note: After Downloading, please read the procedure to jailbreak using redsnow and you should have a jailbroken OS 4.0 iPhone..

This release WILL NOT help you hacktivate or unlock your phone. You’ll need a registered UDID with Apple to get past the activation process. Therefore, DO NOT update to iPhone OS 4 Beta if you rely on an unlock, as upgrading will upgrade your baseband which will leave you locked.