I wish all services, and even a lot of applications, were as good as Dropbox. I turned the participants in my digital humanities seminar onto it, and, if I had done nothing else, I think that alone would have made the class for some of them. *None* of them hauls around a USB drive anymore. They have made sharing Dropbox files and folders part of how they work: it’s been amazing to watch.
If you haven’t tried it out, do. 2GB of storage is free. I have a slightly larger account, 10GB for $10 a month. I keep my home and office files synced via DropBox, and I also access PDFs and other files in GoodReader (iPad) via DB.
If you try it and like it, feel free to use my referral code. We both get an extra 250MB for free.
Once you are up and running, head over to AppStorm and read their “Ultimate Dropbox Toolkit and Guide” (link to post).