JSON Viewer - The most beautiful and customizable JSON/JSONP highlighter that your eyes have ever seen.
Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
JSON Buddy - JSON editor and validator - view, edit and format JSON data
GitZip - Download or create a download link for a GitHub project folder/sub-folder or file.
JSONLint - JSON Lint is a web based validator and reformatter for JSON, a lightweight data-interchange format.
GitHub Hovercard - GitHub Hovercard provides neat hovercards for GitHub.