iPhone software 2.0 is available now for the iPhone—sort of. 

The "unofficial release" is the result of a MacRumors reader combing through the XML of Apple's site. You can download the file directly here. Please use caution with this file, it is not intended for the iPod touch. You have to manually search for the firmware from iTunes by holding down the Option key while clicking the Restore button.

For the cautious, we recommend waiting until the software shows up within iTunes. But for the bold, enjoy!

Apple released iTunes 7.7 late last night and has finally followed it up with the Holy Grail of iPhone software. The fabled iPhone 2.0 software will give the iPhone and iPod touch access to the still-waiting-to-be-launched App Store, which will boast over 500 apps when it goes live. Also, business users will be excited to hear that the IT department can no longer ignore their pleas for iPhone support if they run a Microsoft Exchange service.

Be patient, there is a good chance Apple's servers are being hit pretty hard right now.