What Is This?
This page is for anyone interested in keeping the option to jailbreak the iPhone 3GS with the Dev Team's tools.
The iPhone Dev Team has determined that to do so, you should retrieve a couple of files that are generated by iTunes during the restore process.
You can find more information on their blog, as well as a tutorial to do this manually on Mark's excellent Hack that Phone. website.

The Cat & Mouse Game
Steve Jobs very aptly termed the interplay between Apple and the iPhone Dev Team (and by extension: all jailbreakers) a cat & mouse game.
Things are getting tougher and tougher for the mouse - the mouse needs all the help it can get!

This helper page is free of charge, but since you're already using iFuntastic, why not head over to the Features page and purchase *all* features iFuntastic has to offer? Even with the non-jailbroken iPhone 3GS you can add and remove ringtones, copy video and voice memo recordings and use the iPhone as a USB Storage Device for your own stuff. Thank you for your support!

Let's Get On with It
Apparently there is a loophole in the iTunes restore process that fleetingly produces files in the /tmp directory that are valuable for a future jailbreak.
Rather than try to manually capture them, let your trusty Mac do it for you. Here are the steps to follow: Saved Files