Attention iOS 4.2.1 users: You are now free to jailbreak your iDevice! The hackers at Chronic Dev have come up with an unteathered solution called greenpois0n. Not only can you jailbreak without tethering to the computer but you can also reboot the phone without having to re-jailbreak. Hooray!
The jailbreak is available for Mac, Linux, and Windows. Engadget notes that this version of Greenp0ison was "rushed," so you may want to wait a little before diving in.
You can download the zip file for your system at greenpois0n.com, but be warned that the site is extremely slow in response to all of the downloads.
Update -10:10 PST: One of our bloggers tried Greenpois0n on his iPad running iOS 4.2.1 to no avail. Greenpois0n crashed for him, and he was forced to hard-reset his iPad. He thinks it's because the Greenpois0n servers are slammed right now, so Greenpois0n can't connect to the required database.
Have you tried it? Did you have any problems? Leave a comment or shoot us an e-mail to geektips <at> pcworld <dot> com.