I have been using TouchCopy (review here)for quite a while now to manage my files (images, music, etc..)  It’s a paid service and worth it IMHO. I also really like Files lite (review here) because of the wifi access.  Very cool.

Well, there is now another option for accessing your iPhone like a USB drive, DiskAid.

DiskAid does not have the features of TouchCopy, but if you just want to move files on and off, this will do the job and its free!  This app works for both win and mac (have not tried linux using wine). Nothing to set up, plugin your iphone and you are good to go.  Enjoy!

• DiskAid is a Freeware, 100% free of charge
• PC Windows & Mac OSX compatibility
• Supports iPhone 1, 3G and all iPod Touch
• Auto detection feature, just plugin it in !
• Copy Files & Folders between your iPhone or iPod Touch and your Computer
• Files & Folders Browser
• Drag & Drop
• Features rich file organization including folder creation, renaming… etc.
• No jailbreak needed
• Supported firmware versions : 1.1.1 to 2.1