DirSync Pro (Directory Synchronize Pro) is a small, but powerful utility for file and folder synchronization. DirSync Pro can be used to synchronize the content of one or many folders recursively.
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.