Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
The iPhone doesn't support USB mass storage. Your best option would be something like airsharing, but this wont show as a disc, but allow you to upload and download files through a browser.

There are a couple of software packages (paid for) that will allow you to access your files but I don't recall the names off the top of my head.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.