Found a good one from MacRummors, Where and how to download and install the new iPhone 2.0 version firmware. Yes folks! It is now time to start installing those Apps on your iPhone!
Download the iPhone1,2_2.0_5A347_Restore.ipsw file (download that here)
Now you will need to update your iTunes, in iTunes Store search for "apps" then click on the title of one of the free apps and try to "Get App" this will prompt you to download and upgrade your iTunes. Do so, and run iTunes and plug in your iPhone.
PLEASE FULLY SYNC BEFORE MOVING FORWARD!!!!
You install your iPhone firmware to 2.0 by manually by pressing the "Option key" on your Mac or the "Shift Key" in Windows when you are pressing the "Check for Update" button for your iPhone in iTunes. You can then navigate to where you saved the iPhone1,2_2.0_5A347_Restore.ipsw file and click open. And you are walked thru the remaining steps! It is that easy!
Got iPhone 2.0 Yet?