iPad 3G has been successfully jailbroken. Few hours ago, MuscleNerd of iPhone Dev Team has just tweeted pictures and a video, showing a jailbroken iPad running Cydia. The upcoming Spirit userland jailbreaking software is real and it works. Spirit jailbreak (untethered) works well for the iPhone, iPod Touch and the iPad.
Make sure you have grabbed SHSH Blobs for your iDevice beforehand.