Meta Tags - Meta Tags is a tool to debug and generate meta tag code for any website.
Apple - Available on iOS
Devhints - TL;DR for developer documentation
OpenGraph.xyz - Check how search engines and social medias such as Google, Facebook, Twitter display your website
vvatch.tv - Sit back and watch an endless feed of youtube videos
Meta Tag Generator - Generate HTML code optimal for SEO, social media, & mobile.