Beat egg whites with cream of tartar. Add sugar gradually until mixture holds stiff peaks. Fold in saltines (which have been broken into small pieces) pecans, and vanilla. Bake for 35 minutes in a greased 9x15 pan (I use 9x13) Let cool, spread with 2 packages of dream whip and top with prepared blueberry pie filling. Place in refrigerator for 3 hours.