...I juice them. If I can get 15 limes for a mere dollar, I will buy them. But usually I don't use them all up before they start to dehydrate and brown, so to preserve their freshness I get my little electric citrus juicer out and let it work it's magic. It only took me about 7 minutes to get every last bit of liquid out of the lime halves!
(Photos were taken before she got sick, thus she still has fur on her head.)
The juice gets frozen into tablespoon sized ice cubes and once they're solid I pop them out and store them in freezer bags for when I need them. Super convenient! Most of the time I use a cube or two in my Jamaican jerk marinades or simply in a glass of water. :)