Moments ago, prominent Chronic Dev Team member Joshua Hill (p0sixninja) announced via twitter that "Things have progressed to the point where we don't expect anymore roadblocks. ETA for greenpois0n is 10/10/10 at 10:10:10AM." This hotly anticipated Jailbreak should bring another large contingent into the Jailbreaking community as many new iPhone users who have not been able to jailbreak 4.0.2 and 4.1 will now be able to jailbreak their device.
While details of the jailbreak, such as whether it will be tethered or how it will be implemented have not been announced, that information will likely be given shortly... As a reminder, it is a good idea to save your SHSH blobs with TinyUmbrella if you have not already done so.
UPDATE: Greenpois0n is based on the SHAtter exploit which only works on 4th generation (2010) devices such as iPhone 4, iPad, and the iPod Touch 4. Older devices such as the iPhone 3GS will not be able to use Greenpois0n. Also if you wish to retain your ultrasn0w unlock, you will have to restore to a custom iPSW with baseband 01.59.00 and not the official apple 4.1 since baseband firmware CANNOT be downgraded.