1. Remove seeds and cut rind from cantaloupe. Cut pulp into bite-sized chunks. In blender at low speed, blend cantaloupe chunks until smooth. Pour cantaloupe puree into bowl.
2. In same blender at low speed, blend half of cantaloupe puree, half of vanilla ice cream, and 1/2 cup milk just until smooth. Pour into 2 tall 12-ounce glasses. Repeat to make 2 more shakes.