As there are currently too many iphone devices and jailbreaking method, I will start afresh and only do with iPhone 4 and iPod Touch 4 only.
So here goes:
ios 4.0: http://www.jailbreakme.com
ios 4.0.1: http://www.jailbreakme.com
ios4.0.2: NOT AVAILABLE
ios 4.1: limera1n, greenpois0n
ios 4.2: NOT STABLE YET
NOTE: To preserve your baseband for unlocking, please use tiny umbrella. Tiny umbrella is now updated for ios 4.2 too. Lucky you all iphone 4 users, as it is only for iphone 4 for now.
NOTE: iPhones sold in Singapore are not locked. Therefore, if you bought your iphone from Singapore, you do not need to worry about baseband upgrade. 🙂