Preheat the oven to 325°F. Have ready 8 3 ½ inch pie shells.

Set aside 2 tablespoons of the graham cracker crumbs, then combine remaining ½ cup graham cracker crumbs with sugar. Add melted butter and stir until blended, then divide crumbs among the 8 shells. Press mixture into bottom and up sides.

Set the crusts on a baking sheet and and bake 7 minutes or until crust begins to brown.

Stir sweetened condensed milk, lime zest and sour cream until blended. Stir in lime peel. Pour filling into crusts, dividing evenly. Bake for 7 minutes -- the pies will not appear baked at this point and there may not be any bubbles, but they are most likely done. Let cool completely on wire rack, then chill for at least 2 hours.

To make the topping, beat cream, powdered sugar and vanilla in large mixing bowl with electric mixer on medium speed until stiff. Top pie with whipped cream, then sprinkle pies with reserved 2 tablespoons of crumbs.