Earlier today, Comex has released JailbreakMe 2.0 jailbreak tool for all the iDevices. This new tool helps jailbreakers jailbreak most of the latest firmwares using userland technique.
If you are looking to jailbreak your iPhone 3G, iPhone 3GS or iPhone 4 with JailbreakMe 2.0 tool, go through following guide to understand and perform the steps required to jailbreak the devices running on iPhone 3.1.2, iPhone 3.1.3, iOS 4.0 and iOS 4.0.1.
Note: Even though I’m providing this guide to jailbreak iPhone 4 on iOS 4.0.1, you can use the same guide to jailbreak your iPhone 3G as well as iPhone 3GS.

Guide to jailbreak iOS 4.0.1 on iPhone 4
Requirements:
- iTunes 9.2.1
- iOS 4.0.1 updated iPhone 4
Steps to follow:
1. Back up your iPhone 4 and sync it with iTunes 9.2.1.
2. Connect your iPhone 4 to Wi-Fi connection.
3. Open Safari Browser and navigate to this URL – http://jailbreakme.com/
4. Slide to Jailbreak and wait for the downloading process to complete.
5. Now, JailbreakMe tool will automatically jailbreak the device.
6. That’s it. You will get “Cydia has been added to the home screen” message on the screen.
To unlock your iPhone 3G and iPhone 3GS, check out this guide.
