Per the Dev Center:
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File-Sharing Support
Applications that want to share files with the user can now do so using the file-sharing support in iPhone OS 3.2. Heres how it works:
- An application indicates that it wants to share files by including the UIFileSharingEnabled key in its Info.plist file.
- It puts whatever files it wants to share in its Documents/Shared directory.
- When the device is plugged into the users computer, a mount point is added to the system and the contents of any shared directories appear on the users desktop.
- Users can modify the contents of this directory freely by copying files out, deleting files, or dragging new files in.