[bprater]

Don't forget to nab the UJS plug-in for it:

http://remi.org/2009/01/06/using-firebug-to-debug-unobtrusiv...

Now you don't have to guess what events were bound to which elements!

[LogicHoleFlaw]

That's fantastic. Are there any other great tools I should be aware of?

[davecardwell]

Have you come across Yahoo!’s YSlow plug-in for Firebug? It scores your page against their “Best Practices for Speeding Up Your Web Site”, and is handy for looking at the page’s external resources and relevant HTTP headers.

http://developer.yahoo.com/yslow/

http://developer.yahoo.com/performance/rules.html

[davecardwell]

If you have used YSlow before you might be interested in the upcoming YSlow 2.0. I just came across a slideshow while looking for URLs for my comment above. The extensibility looks quite interesting.

http://www.slideshare.net/stoyan/yslow-20-presentation/

[thorax]

There's also Firephp for getting the server to send additional trace data: http://www.firephp.org/

EDIT:

Also, this article has a good overview of multiple Firebug extensions: http://www.softwareishard.com/blog/firebug/list-of-firebug-e...

I know some people who love PixelPerfect for transferring Photoshop mockups to CSS.

Also one of the comments mentioned widerbug which I might try now that I have this weird 18.4" laptop: http://www.command-tab.com/2008/01/19/widerbug-widescreen-fi...

[Jasber]

FireCookie: https://addons.mozilla.org/en-US/firefox/addon/6683

Great when working with sessions or cookies.

[johns]

I wish I could upvote this 10 times. EDIT: except that while cool, it's very fresh and buggy. High hopes for it though.

[sh1mmer]

This reminds me of something I wrote to do this with YUI.

http://kid666.com/yui-event-list-bookmarklet/

I also wrote a rudimentary Firebug plugin but yours looks way more slick :)