My application creates CSV files, stored in the documents directory, with the purpose of being later imported into Microsoft Excel. What is the best way to transfer these files in an end-user-friendly way, via the iPhone USB cable, to a MacBook? If there is some way to do this exclusively with code on the phone itself (doubtful) that would be ideal. However, I would be amendable to writing a cocoa application for this purpose.
iPhone 3G 3.1.3 MacBook Pro 10.6.2
Transferring files via USB is not officially supported on the iPhone platform and Apple probably won't approve your App if you'd use it: http://techcrunch.com/2010/02/02/apple-stanza-usb/
For now, you should send the files as emails and hope for some kind of file storage support in the next version of iPhone OS.
There is no good way to do this right now. Most applications wind up using WiFi along with some other protocol like WebDav, HTTP POST, AFP, or proprietary ones with a custom app on the Mac.