I have a word doc saved as an attachment in my inbox. I can read it using my iPhone 4S, but I can't edit it, and anyway, I want to edit it on my MacBook Pro. But there is (was) no Internet where I was, and so I couldn't access the file on my computer. Is there any way to transfer the file from my phone to computer using USB?
If you can transfer the document to a general-purpose app that "knows" about files (like GoodReader, Air Sharing, or iBooks), you should be able to access it from the file-handling dialog from within iTunes.
Most computers can create an ad-hoc WiFi network; using this, you'd use a network-sharing app (like Air Sharing) to mount a disk from your iPhone and transfer the files to your computer.
The PhoneView program can read files from iOS devices through USB and get them to your mac in most cases.