DateiSync2010 lets you easily synchronize directories with each other including all subdirectories. You can even configure DateiSync to synchronize multiple directories at the same time if needed. DateiSync works with directories on the same machine but also with synchronizing external drives or drives that are connected with a remote connection. You can even use it for regular backups if you wish.
For professional users, we also provide an advanced pro version at http://jstein-partner.de/Sync/USA