Third-party independent syncing between two or more systems/drives

Does anybody know of a direct syncing software to allow syncing between two or more computers/drives or folders directly?

There's plenty out there i.e. dropbox, box sync.com etc. etc., that offer cloud syncing but all of them are via a third-party web accessible hub service.

For example: using sync.com any files and folders within the default folder "Sync" and wherever on which drive will be synchronized. So e.g. I have on my desktop and on my laptop the same folder with all the contents. Change one item in either it automatically syncs and updates.