These are instructions on how to jailbreak your iPad using Greenpois0n for Mac. Greenpois0n supports iOS 4.1 and iOS 4.2.1.
Open your web browser of choice and navigate to http://www.greenpois0n.com. Click the Mac link at the bottom of the screen.
When prompted save the download to your desktop
Double click the downloaded greenpois0n-osx_rc5.zip file to extract the archive then double click greenpois0n from the desktop to launch the application
Connect your iPad to the computer, power it off, quit iTunes, then click the large Jailbreak button
You will now be instructed on how to place your iPad into DFU mode. You can get help with this here.
You will be asked to press and hold the sleep button for 3 seconds.
Continue holding sleep; press and hold home for 10 seconds.
Release sleep button; continue holding home for 15 seconds.
Once your iPad is successfully in DFU mode the jailbreak will begin.
Click the Complete button once the software application has completed.
You'll notice some verbose mode text scrolling on your device.
After the iPad restarts you'll have a new Loader application on your Springboard. Press to launch it.
Press to select Cydia then press the large Install Cydia button that appears.
Once Cydia has installed successfully you can remove Loader from your device. Press the Options button then press the Remove Loader.app button.
Reboot your iPad then run Cydia. Let it do all the necessary updates.
***A big thanks goes everyone who made this jailbreak possible.