According to the source
http://www.treasurydirect.gov/govt/reports/pd/histdebt/histdebt.htm
the total debt outstanding has grown as follows:
09/30/2006 8,506,973,899,215.23
09/30/2005 7,932,709,661,723.50
09/30/2004 7,379,052,696,330.32
09/30/2003 6,783,231,062,743.62...