My vivacious and charming friend Samuel Goodwin has just released a new app for formatting JSON called Formatter on the Mac App Store for the low price for $4.99. You can drag and drop JSON files right on it, or use the included Xcode plugin to turn your gross mess of brackets and parenthesis into artisanally crafted pretty printed JSON files. Another thing I like about Formatter is that it includes a QuickLook plugin to make looking at JSON in the Finder a bit nicer.
The pasta maker icon is pretty clever, too. Go buy it.