This fantastic little utility runs seamlessly on Mac OS X, Linux and even Windows. It is fantastic for anyone looking for a simple way to backup, share files, create photo albums and/or sync files between multiple computers that they use (say a work or home computer). After a file is saved to your dropbox, it is automatically synced to all machines that are linked to that drop box.
They desribe their tool as:
Dropbox is the easiest way to store, sync, and, share files online. There’s no complicated interface to learn. Dropbox works seamlessly with your operating system and automatically makes sure your files are up-to-date. Available for Windows, Mac, and Linux.
https://www.dropbox.com/