Wappalyzer - Wappalyzer is a technology profilers and leads data provider. Create lists of websites and contacts that use certain technologies.
Reddit List - Tracking the top 5000 subreddits
BuiltWith - Find out the technology behind websites
Reddit Check - A tool to check if a URL is on Reddit and going viral
WhatRuns - Extension that helps you identify technologies used on any website at the click of a button.
University of Reddit - Learn 1,000's of new things, from reddit