Firebug
Web Developer
Pixlr Grabber
FireFTP
ColorZilla
Codetch
Greasemonkey
FireShot – Webpage Screenshots: Capture + Annotate
MeasureIt
GridFox – The Grid Layout Firefox Extension
OperaView
Window Resizer
IE Tab
Palette Grabber
Console⊃2;
Font Finder
IE NetRenderer
Yahoo! YSlow for Firefox
SeoQuake SEO extension
Total Validator
Server Switcher