I just found a very simple but effective viewer for JSON files: not only it can display their structure, but also reformat it (but then you have to copy+paste result to RJ TE). It's open source and can be freely downloaded from http://jsonviewer.codeplex.com/
JSON Viewer
JSON Viewer
Alium tibi quaere fratrem; hic, quem tuum putas, meus est. Titus Flāvius Caesar Vespasiānus Augustus
Re: JSON Viewer
JsonEdit is a better one:
http://tomeko.net/software/JSONedit/
http://tomeko.net/software/JSONedit/