I posted about this is the kitchen equipment forum when I was looking for a citrus juicer recommendation, but this forum doesn't seem to be getting much love so I'll post the actual recipe here. Cafe Rio is a Mexican restaurant chain out west that has several drinks made fresh in the restaurant each day. My favorite is the mint limeade. It really hits the spot on a hot summer afternoon. This is an approximation of their recipe.

Zest from 4-5 limes
2-3 sprigs of mint (spearmint, not peppermint)
1-3/4 cups sugar
2 cups water
1-1/2 cups fresh squeezed lime juice (about 12 limes)
8-10 cups water
Leaves from 3-4 sprigs of mint, roughly chopped or crushed

Zest 4-5 limes using a Microplane-type grater. Mix zest into sugar and allow to sit for several hours to a day.
Combine lime sugar, 2-3 sprigs of mint, and 2 cups water in a small saucepan. Bring to a boil. Continue boiling for five minutes. Turn off heat and allow to cool. Strain out the mint sprigs and most of the zest. (Some zest will likely pass through. That's okay.)
Squeeze limes to get 1-1/2 cups of juice. Citrus juices are always better if left to sit for at least several hours. Cover and store in refrigerator until ready to use.
Combine cooled mint/lime syrup, lime juice, chopped mint leaves, with 8 cups of water. Add more water to taste, bearing in mind it will be watered down further if you serve it over ice.

If you want to get fancy, make up some more lime sugar, moisten rim of serving glass, lightly press into lime sugar. Garnish with additional mint leaves.

The pitcher I use to make this isn't large enough for a full recipe so I add only four cups of water and then add additional water when serving. This works well except for when my nephew decides to try it without asking and drinks the concentrate straight up. That's one way to keep him out of my mint limeade.