The Simple Postcard - Text a photo to mail it as a postcard
BuiltWith - Find out the technology behind websites
Mailjoy - Delightfully easy direct mail marketing. A DIY direct mail tool created for marketing and growth teams. Design, mail & track personalized direct mail postcards and letters. Digital marketers use Mailjoy to send data-driven mail campaigns.
Wappalyzer - Wappalyzer is a technology profilers and leads data provider. Create lists of websites and contacts that use certain technologies.
MailtoUI.js - Enhance your mailto links with a convenient user interface.
What CMS - WhatCMS.org looks at a variety of factors within a webpage to determine what CMS a website is using.