BuiltWith - Find out the technology behind websites
Pudding.ai - Real-time ad creative analysis solution that helps marketers to easily understand ad creative performance with actionable insights.
Wappalyzer - Wappalyzer is a technology profilers and leads data provider. Create lists of websites and contacts that use certain technologies.
AdWhistle - AdWhistle is a web-based platform that provides you the features and tools to create a campaign strategy and run the ads successfully on various social media platforms.
What CMS - WhatCMS.org looks at a variety of factors within a webpage to determine what CMS a website is using.
Facebook Ad Library - Find out who is paying for ads with Facebooks new tool