You can't currently use your iPhone as a storage device, but FileMagnet solves that problem. What's more, it's not just a way to copy files to your Mac, but to view them too. Only the most common filetypes can be viewed – JPEG, GIF, TIF, PNG, HTML, RTF, RTFD, DOC, TXT, PDF, iPhone-compatible movies and audio files, Excel, PowerPoint – but anything can be copied across, and that should suffice for most folks; iWork support is coming. Files are added with a clever Bonjour-aware uploader app on your Mac.
Launch the app on your Mac and iPhone, and so long as they're on the same wireless network they'll be automatically linked. Much better than emailing stuff to yourself, and very polished, too. Could be faster, mind, and it balked at some Excel spreadsheets.