1In large bowl, beat butter and 1/2 cup of the powdered sugar with electric mixer on medium speed 3 minutes or until fluffy. Stir in vanilla, limeade concentrate and lime peel. On low speed, beat in flour, graham cracker crumbs and salt just until blended. Fold in nuts. Cover; refrigerate 1 hour.
2Heat oven to 400°F. Shape dough into 36 (1 1/4-inch) balls. On ungreased cookie sheets, place balls 1 inch apart.
3Bake 8 to 10 minutes or until slight cracks appear and cookies are lightly golden. Remove from cookie sheets to cooling racks; cool 5 minutes. Place remaining 1 cup powdered sugar in shallow dish. Roll warm cookies in powdered sugar; cool. Store tightly covered up to 1 week.