Dropbox - Online Sync and File Sharing
Link Shell Extension - Link Shell Extension (LSE) provides for the creation of Hardlinks , Junctions , Volume Mountpoints...
Google Drive - Access and sync your files anywhere
FileMenu Tools - FileMenu Tools lets you customize the context (right-click) menu of Windows Explorer.
ownCloud - ownCloud is an open source project enabling businesses to host their own cloud storage while maintaining regulatory and compliance needs.
Symlinker - Symbolic Link Creator. GUI for mklink, Microsoft Windows symlink utility