Mac OS X only: Disk for iPhone is a free application that mounts your iPhone or iPod touch as a drive on your Mac, turning your device into a portable hard drive. Disk for iPhone requires that you've already installed the very cool, previously mentioned MacFUSE—which, among other things, allows you to mount any file system on your Mac over SSH. Assuming you've done that, just plug in your iPhone or iPod touch, run Disk for iPhone, and get browsing. The app runs in your menu bar, and your iPhone should show up as a drive on your desktop the same way a USB drive does when you plug it in. Disk for iPhone is a free download, Mac OS X only. For full read/write access, you'll need to jailbreak your iPhone. It's a good option for Mac users, but if you're on Windows or don't want to jailbreak, previously mentioned DiskAid does the job nicely. Then again, with native iPhone apps like the Air Sharing (original post), these desktop-based apps may no longer seem all that necessary. If you're using your iPhone as a portable disk, let's hear what method you're using in the comments.