1 12 oz. can frozen limeade (storebrand is fine)
1 cup tequila (not too cheap, but save the expensive stuff for sipping)
1/2 cup triple sec or Cointreau
Salt for rim (optional)
Put the limeade, tequila, and triple sec into blender. Fill with ice. Blend on highest setting until a slushy consistency.
Please note: These are seriously strong. If desired, give the first margarita to the person who needs it the most, then add more ice to fill the blender and slush again.