In a medium bowl, toss cranberries with 1 tablespoon of lime juice. Drain the lime juice, then toss the cranberries with 2 tablespoons of sugar. Spread them out on a baking sheet to dry.

Mix the remaining sugar with salt on a shallow plate. Use the lime wedge to wet the rim of each glass, then dip it in the sugar-salt mixture.

In a large blender, combine cranberry juice, tequila, triple sec, remaining 1/2 cup lime juice, and ice. Blend until smooth. You may need to do this in batches.

Pour the mixture into the prepared glasses and garnish each with a sprig of mint and a few sugared cranberries. Enjoy your festive margaritas!