We covered using your phone as a USB storage device awhile ago. It's one of those features that lots of folks want but the demand waxes and wanes, usually based on remembering that our phones can't do it natively. For the record, Microsoft always frowned upon this practice as you could theoretically screw something up. We're not even sure if the original hack works anymore (we're betting 'no') but that hasn't stopped developer Den Delimarsky from coming up with his own solution.
His method is detailed in full in this post and we'll leave the nitty-gritty to the developers out there. As he says, you can do this yourself though for us non-techies he's looking to release this publicly when it's all good and ready (at least we really hope he does).
"You probably always wanted to use your Windows Phone device as a USB storage device but never could. Well, this is solvable. There were a couple of hacks floating around, but I was curious to see if I can do it by myself. Well, I found a way to do it without third-party OS hacks and only with the help of a simple application built around the Microsoft.Smartdevice.Connectivity assembly.
I am not releasing the application itself at this point because there is more work to be done, but you can take a peek at what it looks like."
You can even upload files to an app's isolated storage, which is a bit advanced for most of us. Just form glancing at the tool this certainly seems like a much nicer method than before and looks quite promising. While not a plug-n-play solution, probably something we won't see anytime soon, it could be a decent option for those who need such a method for file transport.