Blackbird

Blackbird offers a dead-simple way to log messages in JavaScript and an attractive console to view and filter them. You might never use alert() again.

The code (blackbird.js, blackbird.css) and image assets (blackbird_panel.png, blackbird_icons.png) were created by G. Scott Olson.

The concept for Blackbird was sparked by JavaScript Logging, an article by David F. Miller. The first iteration of this project, named jsLogger, was developed for internal use at Orbitz. In the fall of 2007, jsLogger was rewritten from the ground up, given a facelift, and named project Blackbird.

http://www.gscottolson.com/blackbirdjs/