BuiltWith - Find out the technology behind websites
Competitive Heatmap Analysis - Any website's heatmap data is at your fingertips
Wappalyzer - Wappalyzer is a technology profilers and leads data provider. Create lists of websites and contacts that use certain technologies.
WebGazer.js - Eye tracking on the browser
What CMS - WhatCMS.org looks at a variety of factors within a webpage to determine what CMS a website is using.
FOVE - An eye tracking virtual reality headset (pre-launch)