Microsoft's Windows Live FolderShare to backup your file

Access your file at home from office with Microsoft's Windows Live FolderShare, which syncs files across the Internet (and does so automatically). Microsoft's Windows Live FolderShare advantage is that you can expand your backup network to include friends, syncing critical files to their machines and vice-versa. Microsoft's Windows Live FolderShare costs nothing to use. Microsoft's Windows Live FolderShare can sync files up to 2 GBs in size. And it works on both Mac and PC.
For offline way to back up your file use SyncToy 1.4