Annotable - Ultimate image annotation & markup tool
BuiltWith - Find out the technology behind websites
Weava - Workspace to highlight, organize & collaborate on your research articles.
Wappalyzer - Wappalyzer is a technology profilers and leads data provider. Create lists of websites and contacts that use certain technologies.
Airsketch - Simple screenshots + annotations for Mac 🖥️
What CMS - WhatCMS.org looks at a variety of factors within a webpage to determine what CMS a website is using.