Yet another new feature in Gmail Labs to report: a “send and archive” button, that, when enabled (from the “Labs” page under “Settings”), allows you to reply to a thread and have it immediately archived.
Like all archived messages, these threads will still be available in the “All Mail” folder of Gmail, which also includes labeled messages that you filter out of the Inbox.
One important feature still missing from “Send & Archive” is an “Undo,” so you can move a message back to the Inbox without having to go into the All Mail view, as you can currently do when you archive something from elsewhere in Gmail. On the Gmail blog, the engineer who built the feature indicates that this will be available “in the coming weeks.”
Turn on "Send & Archive" from the Labs tab under Settings, and you'll see a new button in the compose form labeled “Send & Archive”. The button does what it says: it sends your reply and then archives the thread with one click.
