BuiltWith - Find out the technology behind websites
Nacho Analytics - View any company's analytics
Wappalyzer - Wappalyzer is a technology profilers and leads data provider. Create lists of websites and contacts that use certain technologies.
ChatWhale - Gamify your customer communication and loyalty rewards
What CMS - WhatCMS.org looks at a variety of factors within a webpage to determine what CMS a website is using.
Social Insider - Get an inside view of your competitors' Facebook activity