A new Gmail Labs feature “Mark Unread From Here,” when enabled from the Labs tab under Settings, display a new “Mark unread from here” option in the drop down menu found in the upper right-hand corner of messages. Clicking this option on a message tells Gmail that you want that message to be the first one you see when you reopen the thread later, with all messages after it open for easy reading. So, when you leave partway through reading a long thread, figuring out where to start reading again is easy.
