iPhone 3.0 is live! so we are going to repost our tethering tutorial with some big improvements. You now don't have to do any downgrading or torrenting. Seems you can just run a little command in terminal (Make sure you are on OS 3.0 on a 3G iPhone and iTunes 8.2):
defaults write com.apple.iTunes carrier-testing -bool TRUE
After that, the steps become a lot more simple.
2. Option-click on "restore" in your iTunes with your iPhone attached. Browse to the opened disk image file and hit OK. It will update phone settings for a few seconds.
3. You have tethering. Now go into your iPhone/settings/general/network/Internet Tethering and turn it on.
Boom - 3 steps to tethering...
Oh, and how to you like cut and paste and spotlight search?