You don't need any software. Like all good media players, it works as a USB mass storage device. You can just connect it to any computer, copy whatever files you want to it just as if it were an external hard disk or flash drive, and when you disconnect it it automatically finds the files and indexes them for the relevant applications.

That said, if you want them, there are (from what I hear) good file syncing options if you want them. DoubleTwist, Salling Sync, The Missing Sync, and presumably more on the way.