pivot table

http://www.cpearson.com/excel/pivots.htm
http://www.ozgrid.com/Excel/excel-pivot-tables.htm
http://peltiertech.com/Excel/Pivots/pivotstart.htm
http://www.exceltip.com/excel_tips/Excel_Pivot_Tables/32.html
http://www.mrexcel.com/archive/Pivot/index.html
http://www.exceltip.com/excel_tips/Excel_Pivot_Tables/32.html