Simple Inbox Archiving Script for Apple Mail

gistfile1.scpt

-- See article here: http://daringfireball.net/2007/07/simple_inbox_sweeper

-- The following should be one long line:
set _description to "All unflagged, read messages in each IMAP account 
    inbox will be moved to the “Archive” mailbox corresponding to that  
    account. This action is not undoable."

tell application "Mail"
	display alert "Archive read messages from IMAP inboxes?" buttons ¬
		{"Cancel", "Archive"} cancel button 1 message _description
	
	repeat with _acct in imap accounts
		set _acct_name to name of _acct
		set _inbox to _acct's mailbox "INBOX"
		try
			set _archive_box to _acct's mailbox "Archive"
		on error
			display alert "No “Archive” mailbox found for account “" & ¬
				_acct_name & "”."
			return -- Stop the script
		end try
		
		-- Begin update for OS X 10.7.0
		set _msgs_to_move to (a reference to ¬
			(every message of _inbox ¬
				whose flagged status is false and read status is true))
		set _msg_list to contents of _msgs_to_move
		if (_msg_list's length > 0) then
			move _msgs_to_move to _archive_box
		end if
		-- End update for 10.7.0
		
	end repeat
end tell

If you want to go full integration you can add this as a "Service" from Automator - and attach a keyboard shortcut - since apple removed the scripts menu from Mail.app a few versions ago.

http://culturedcode.com/things/wiki/index.php/Creating_a_service_for_Mail_in_Snow_Leopard

Process is more or less here - just choose "run applescript" as the sole action and use the snippet above.

@jerrod Assuming it still exists in Lion, you can use the system script menu (in Snow Leopard, it's a preference in AppleScript Editor). You can also use FastScripts.