This post has been a long time coming. It was surprisingly easy to jailbreak / unlock the iPhone 3g to the 2.2.x firmware and now amazingly simple to move to the 3.0 firmware. A big thanks Dev Team for making this available for free, simply phenomenal what these guys are doing. 
The actual process though can get a little intimidating, but iClarified takes even that mystery out of the unlock. NOTE: These steps work, but please do them at your own risk. If something goes wrong, there is no support. 
Firmware Files are here. 
NOTE: When you save the files, they tend to save as zip files, rename them to .ipsw and it works just fine, seems like a browser thing. 
1. Jailbreak your 3g iPhone. Works with any carrier in India / US. Verified in both locations.
2. Now, once the Jailbreak has occurred, follow the unlock steps by Dev Team here. 
3. Enjoy!
   If you own a 2g, then its even simpler, the jailbreak process wil do the unlock as well. Follow steps here.
   The above steps I've exercised on a 2g and 3g phone and so far they work pretty well.  This post is as-is and author takes no responsibility. I spent some time tracking down these steps online - thought it would help others to collate them in a single location.Good luck and enjoy the iPhone!
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