Hardware/Software:
[*]Frozen concentrated juice of any flavor,
[*]1/3rd of normal amount of water,
[*]2/3rd of that water used in the form of ice.
[*]Blender.
Directions:
[*]Combine.
[*]Blend.
Additives if you want something a bit better but a bit more work:
[*]A tablespoon of sugar for the tart juices (not needed for grape juice or orange juice),
[*]A tablespoon of lemon/lime juice for the sweet juices (really makes grape or orange juices great),
[*]A few shots of your favorite alcohol.
Whole thing takes just 2-3 minutes if you have a good blender. 5-10 with a crappy blender.