A Firefox extension to detect memory leaks caused by JavaScript. It pops up an alert dialogue when windows close if there is code still pointing to JavaScript objects.
JavaScript documentation surrounding version 1.5, 1.6 (supported by Firefox 1.5 and Mozilla 1.8), and version 1.7 (supported by Firefox 2.0). Backed up by mailing lists, newsgroups and an IRC channel
Joe Hewitt, in this Dr Dobbs article talks about using the Firebug extensions to inspect and debug Ajax applications (or any browser-based JavaScript application). It also has CSS inspecting capabilities, editing JavaScript on the fly, inspecting HTTP request and responses, logging, breakpoint debugging and profiling. A useful howto.
Svend Tofte puts together a detailed guide to setting up and using the Venkman debugger. From basic debugging to watchlists and call stacks, breakpoints, and more advanced techniques like meta comments and profiling. It also contains a list of other useful Venkman resources.
Apart from being an elegant debugger, FireBug offers the developer hooks that can be used from JavaScript, offering logging, assertions, performance measuring, and command line functions for inspection or traversing a document.
Building extensions for Firefox 1.5. The Firefox and Mozilla platforms keep changing the extensions enough to out-date tutorials. This is the official documentation, covering the directory structure, the manifest, XUL Overlays, chrome URIs and packaging
A collection of gotchas and guidance in Greasemonkey scripting. Positioned as an addition to Mark Pilgrim's dive into Greasemonkey
Mark Pilgrim's essential online book about developing Greasemonkey scripts. Excellent starting point for Greasemonkey developers. Covers everything from setting up a Greasemonkey scripts to common DOM coding idioms, as well as a brief rundown of XPath, and case studies of Greasemonkey scripts.
Mark Pilgrim dissects the security issues of the 0.3 Greasemonkey, and describes how the new architecture of Greasemonkey works, pointing out pitfalls and how to address them.
All of the tools you need to poke, prod, and monitor your JavaScript, CSS, HTML and Ajax are brought together into one seamless experience, including a debugger, error console, command line, and a variety of fun inspectors.