iPhoneDrive lets you use iPhone for file storage
Ecamm Networks has released iPhoneDrive, a Mac OS X application that enables you to move files back and forth between your Mac and your iPhone. It costs $9.95; a free demo is available for download.
The iPhone already synchronizes content with the Mac including contact and calendar information, music and video, but unlike the iPod, it can’t be mounted as a mass storage device for you to put files on it. iPhoneDrive overcomes that limitation.
The software lets you drag and drop individual files to be copied onto the iPhone. You can also use the iPhoneDrive toolbar to facilitate data transfers, or copy over entire folders.
System requirements call for Mac OS X v10.4.10 or later, iTunes 7.3 or later, a Mac equipped with USB 2.0, and, of course, an iPhone.