Em 2006 publiquei um post listando algumas extensões que recomendava para o Firefox, o tempo passou e acabei mudando de browser também. E o mais engraçado é que mesmo mudando de browser, as duas extensões que sempre fiz questão de instalar no Firefox, hoje também são pré-requisitos no Chrome. São elas:
Firebug Lite is not a substitute for Firebug, or Chrome Developer Tools. It is a tool to be used in conjunction with these tools. Firebug Lite provides the rich visual representation we are used to see in Firebug when it comes to HTML elements, DOM elements, and Box Model shading. It provides also some cool features like inspecting HTML elemements with your mouse, and live editing CSS properties.
The Web Developer extension adds a toolbar button to the browser with various web developer tools. This is the official port of the popular Web Developer extension for Firefox written by the same person.
Além dessas que considero obrigatórias, recomendo também as seguintes extensões:
Valida e formata páginas com conteúdo JSON. Excelente extensão.
This extension allows developers to put a semi-transparent image overlay over the top of the developed HTML and perform per pixel comparison between them. Analogue of popular Firefox extension PixelPerfect.
Silver Bird (utilizava o Tweetdeck até ser necessária a criação de uma outra conta)
Silver Bird is an awesome Twitter client extension for Google Chrome with lots of features.
It's easy to use this extension to capture visible content of a tab, a region of a web page, or the whole page as a PNG image.
Show a warning dialog when closing a window containing multiple tabs.