Csync is a lightweight utility to synchronize files between two directories on
a system or between multiple systems.

It synchronizes bidirectionally and allows the user to keep two copies of files
and directories in sync. csync uses widely adopted protocols, such as smb or
sftp, so that there is no need for a server component. It is a user-level
program which means you do not to be a superuser or administrator.

WWW: http://owncloud.org/sync-clients/