Visual Studio: JSON visualizer when debugging
Yes, use this addon on Codeplex.
Overtly visible disclamer: I wrote this and I'm giving it away for free via Microsofts Visual Studio Gallery. No ads, no link to my own site or anything.
I found this thread when looking for the exact same thing but seeing that http://jsonviewer.codeplex.com/ is "A visualizer for Visual Studio 2005" i felt that it was probably to outdated for my use. So I wrote a new visualizer instead (with built in jsonlint-support!). It has been tested with Visual Studio 2012 (but probably works fine for at least 2008 and 2010) and available from Microsofts Visual Studio Gallery.