Simultaneous jailbreak on the iPhone 4, iPhone 3GS and iPad using Jailbreakme. This jailbreak is done directly on your phone using Safari, so you do not need to connect it to the PC. Total time is under 5minutes.
On safari, go to http://Jailbreakme.com, slide to Jailbreak and enjoy.
This works on almost all devices running the latest software as of August 1st, 2010. In the video we use an iPhone 4 running iOS 4.0, iPhone 3GS running iOS 4.0.1, and an iPad running iOS 3.2.1.