Dropbox has become my replacement for USB thumb drives. It functions in the cloud, but unlike the iDisk and other remote storage technologies. Instead of mounting a drive to hold your files, you download and install a small application. The application places a folder on your desktop, the contents of which are synced to online storage automatically. Once installed on multiple computers and devices (e.g., the iPhone), you always have your updated files at hand. And when you're on someone else's computer, you can access your files via a web interface. It's slick, and it's free. You pay for extra storage space over the first 2GB.
