In the bottom of a greased 15" x 10" jelly roll pan, arrange graham crackers in a single layer with sides touching.  Sprinkle nuts evenly over crackers.  In a small heavy saucepan, combine butter, brown sugar and cinnamon.  Stirring constantly, cook over medium heat until sugar dissolves and mixture begins to boil.  Continue to boil syrup for 3 minutes longer with stirring; pour over crackers.  Bake at 400 degrees for 8 to 10 minutes or until bubbly and slightly darker around the edges.  Cool completely in pan; break into pieces.  Store in an airtight container.