Update (10/05/2009): There is now another tool to downgrade your iPhone 3G’s baseband.
Finally, at last! A baseband downgrade tool for iPhone 3G. Readers who are iPhone 3G users who unexpectedly and accidentally upgraded their iPhone 3G’s baseband during the iPhone firmware 2.2.1 update will be happy to know that ModMyi (not the iPhone Dev Team) have come up with a tool that claims to downgrade your iPhone’s baseband from 02.30.03 back to 02.28.00.
While back in February, the iPhone Dev Team did specifically release a Pwnage Tool for iPhone 3G users so