Reddit List - Tracking the top 5000 subreddits
BuiltWith - Find out the technology behind websites
Upvoted - A news publication by reddit
Wappalyzer - Wappalyzer is a technology profilers and leads data provider. Create lists of websites and contacts that use certain technologies.
Mailbrew - Automated email digests from Twitter, Reddit, YouTube & more
What CMS - WhatCMS.org looks at a variety of factors within a webpage to determine what CMS a website is using.