Can I tether with my iPhone 4 without jailbreaking my phone or paying for the additional service? Basically, I want to be able to tether my laptop to my iPhone 4 but I don't want to pay for extra service or lose my unlimited plan.  I've heard there were some apps that had easter eggs but are no longer available.  I've also heard that you can do some things if you have a developer account.

So, are there any free, simple ways to do this without jailbreaking my phone?
It's probably not an easy way but since there have been some apps snuck into the app store that had hidden tethering abilities: http://www.wired.com/gadgetlab/2010/07/apple-approves-pulls-flashlight-app-with-hidden-tethering-mode/ It's clearly possible to do this in an app but not one that will be in the official store. One way around this would be to spend the $99 for a developer account, find some source code, compile it and install it onto your device. Don't mind the hand waving around finding appropriate source code though.