Redsnow / Redsn0w helps to Jailbreak your latest Apple’s iPhone 3G iOS .
also iPhone 4.0 Beta iOS Jailbreak can be done with RedsnOw 0.9.5.
All available Download Links for redSn0w 0.9.5 to jailbreak iPhone
Here is a Tutorial Video which shows how you could Jailbreak iOS 4 & Unlock iphone 3g and Jailbreak iPod Touch 2nd gen
Complete Instructions/ Tutorial to Jailbreak iPhone 3G iOS4 using Redsnow 0.9.5