iPad 3G has been successfully jailbroken only within a few hours of its launch. MuscleNerd of iPhone Dev Team has just posted couple of pictures and a video, showing a jailbroken iPad running Cydia. The upcoming Spirit userland jailbreaking software is the tool which is said to have been used to achieve this.
For all the doubters out there, this only means one thing. The untethered all device (iPhone, iPad and iPod touch) userland jailbreak is just around the corner. Make sure you have grabbed SHSH Blobs for your iDevice beforehand. A step by step guide for which can be found here.
Here is a short video which shows Cydia running on iPad 3G.