Chrome Extensions

Pixir Editor - photo editor
ColorZilla - color reading
WhatFont - identifies fonts
Amino - live CSS editor
Stylebot - customized CSS for any site
EnjoyCSS - CSS3 generator
Dimensions - measures items on screen
Eyedropper - picks colors
BuiltWith - IDs technology stack of a website
Naptha - image-to-text editor

Web Dev Checklist - best practices
Checkbox - website SEO/speed/security auditor
Web Dev - dev toolbar button
StayFocusd - limits time on specified sites